Estimate Cubic Yards, Concrete Bags & Material Cost for New Hampshire Projects
Use the Concrete Calculator in New Hampshire to estimate concrete for slabs, patios, driveways, parking pads, footings, piers and multi-section pours. Get cubic feet, cubic yards, bag quantity, ordering allowance and optional ready-mix material cost.
Choose the project geometry that best matches the finished concrete.
Estimate a rectangular patio, slab, walkway section, pad or similar flatwork project.
Use the thickness required by your plan or project requirements.
Enter the actual product yield.
Optional: enter a current supplier quote.
Verify actual formed dimensions, project requirements and supplier ordering increments before purchasing concrete.
Calculate a private driveway slab plus a separate apron, flare or approach area.
Quantity estimate only. It does not approve driveway access geometry, right-of-way construction or permit status.
Estimate concrete for approved square-pad or round footing/pier dimensions.
Material quantity is not structural design.
Add up to three rectangular sections with different dimensions and thicknesses.
Avoid overlapping sections or the same concrete area will be counted more than once.
A Concrete Calculator in New Hampshire should begin with the dimensions of the concrete you actually intend to place. That sounds simple, but many quantity mistakes happen because estimators use excavation width, property dimensions, a rough sketch or a generic “typical” quantity instead of the finished concrete geometry. This page keeps the math transparent: measure the shape, enter the required thickness, calculate exact volume and then choose an appropriate ordering allowance.
The same basic volume formulas work across New Hampshire neighborhoods, but project requirements do not. A backyard patio, driveway approach, structural footing, garage slab and sidewalk repair can fall under different construction and permitting rules. For that reason, the calculator handles quantity while linking to current New Hampshire resources for permit and right-of-way questions.
The page also avoids hard-coding a local ready-mix price. Concrete prices can change with supplier, mixture specification, order size, delivery zone, fuel, short-load policy and access. Enter your current New Hampshire quote if you want a simple concrete-material budget.
For a rectangular slab, multiply length by width to get square feet. Convert concrete thickness from inches to feet by dividing by 12, then multiply the area by thickness to get cubic feet. One cubic yard contains 27 cubic feet, so divide by 27 for cubic yards.
Cubic yards = cubic feet ÷ 27. Order estimate = exact cubic yards × (1 + allowance percentage).
Suppose an New Hampshire patio is 20 ft long by 12 ft wide and the approved thickness is 4 inches. The area is 240 ft². Four inches equals one-third of a foot, so the exact volume is 80 ft³. Divide 80 by 27 and the result is about 2.96 yd³. Add 10% in the calculator and the planning order becomes about 3.26 yd³.
Use final form dimensions whenever possible. Rechecking after base preparation can catch meaningful differences between the design sketch and the concrete that will actually be placed.
Patios, walkways, equipment pads, small shop slabs and other flatwork can usually be estimated as rectangles or a collection of rectangles. Measure the inside distance between forms, not the total excavated area. Excavation often extends beyond the concrete edge to make room for base preparation and forming.
If the project changes thickness, split it into separate areas. For example, a patio slab may be one thickness while a thickened edge, equipment pad or stair landing is deeper. Increasing the whole slab thickness to compensate for a small deep area can overstate the order.
The Slab & Patio calculator displays gross square feet, exact cubic feet, exact cubic yards, allowance-adjusted order volume, estimated bags and optional material cost. For garage-specific planning, see the Concrete Garage Floor Calculator.
A New Hampshire driveway can contain a private slab, widened parking area, garage approach, apron and other transitions. The second calculator separates the main driveway and apron so different widths or thicknesses are not hidden inside a single average rectangle. Enter the dimensions that match the finished concrete shown on the plan or approved layout.
Permit, zoning and driveway-access requirements can vary by municipality and road authority. New Hampshire’s state building-code statute reserves permit issuance and local enforcement functions to qualifying local jurisdictions, while the applicable state building code establishes minimum construction requirements. A driveway project that connects to a public road can also have access or right-of-way requirements that are separate from the concrete quantity calculation.
Use the calculator for material volume, then confirm local requirements with the town or city that has jurisdiction over the property. For a more detailed quantity breakdown, use the Concrete Driveway Calculator.
New Hampshire RSA 155-A establishes the state building code and requires buildings and structures constructed in the state to comply with that code. As currently adopted, the state building code references the 2021 International Building Code, 2021 International Residential Code and related 2021 model codes, together with the adopted New Hampshire amendments and the 2023 National Electrical Code.
RSA 155-A:4 requires a permit before starting new construction or renovation of buildings and structures described by the statute. In municipalities that have adopted an enforcement mechanism, the permit follows the locally adopted process. This means a statewide concrete calculator cannot tell a homeowner in Concord, Manchester, Nashua, Portsmouth, Keene or a small town which forms, reviews or fees apply locally.
Use the official New Hampshire Building Code statute and your local building department or code official to verify the process for the exact property and scope.
Footing concrete should be calculated from approved dimensions. The Footing & Pier mode supports either a square pad or a round cylinder. A square footing uses side × side × depth. A round footing uses π × radius² × depth. Multiply one-unit volume by the number of identical footings.
This calculator intentionally does not determine required footing size. New Hampshire structural projects can be influenced by building loads, soil conditions, seismic design, reinforcement, nearby slopes, retaining conditions and other factors that cannot be reduced to a universal internet dimension.
For preliminary bearing-area concepts, see the Concrete Foundation Size Calculator. For deck support, see the Concrete Deck Footing Calculator. Final structural dimensions should come from the applicable prescriptive provision or approved design.
An ordering allowance gives room for modest differences between theoretical and field volume. Base elevation may vary slightly, forms can move, hand excavations are not perfectly smooth and some concrete remains in placement equipment. The correct allowance depends on the project rather than the city name.
A carefully formed slab on a uniform prepared base may need less contingency than hand-dug footings, irregular demolition replacement or a complex driveway transition. The calculator lets you choose your own percentage. Measure accurately first and use allowance second.
Supplier ordering increments also matter. If the calculator produces 6.37 yd³, the actual order may be rounded according to the supplier’s accepted increment and your project conditions. Confirm that policy before delivery.
The cost field intentionally starts at zero. Enter a current ready-mix quote per cubic yard from the supplier serving your project. The calculator multiplies that rate by the selected order volume, including your allowance.
The result is not an installed concrete price. A complete project budget may include demolition, excavation, haul-off, grading, base rock, compaction, forms, reinforcement, dowels, anchors, vapor retarder, pumping, labor, finishing, curing, saw cutting, sealer, traffic control and permit fees.
Use the current quoted cubic-yard rate for the actual mixture.
Add short-load, fuel, pump, waiting-time or difficult-access charges separately.
Budget base, forms, reinforcement, labor, finishing and curing outside the material calculation.
Bagged concrete can be useful for fence posts, isolated footing pads, small landings, patch areas and other low-volume work. The bag calculator uses the yield you enter because bag weight alone does not tell you the exact cured volume. Different products and package sizes can have different yields.
If a project needs 12 ft³ after allowance and the selected mix yields 0.60 ft³ per bag, the calculation is 12 ÷ 0.60 = 20 bags. If the yield is 0.45 ft³ per bag, the same project requires about 27 whole bags.
For larger slabs and driveways, compare bagged-concrete labor with ready-mix delivery. Hundreds of bags can create a difficult placement sequence and increase batching variability.
New Hampshire properties can include rural lots, sloped sites, older homes, additions and renovation work that produce irregular concrete layouts. The safest estimating method is to split the project into simple non-overlapping shapes. An L-shaped patio can become two rectangles. A widened parking area can become several rectangles. A triangular taper can be calculated separately as one-half × base × height × thickness.
The Multiple Sections calculator supports three rectangles and lets each section have its own thickness. If you have more sections, calculate them in groups and add the exact volumes before applying one final allowance.
For other geometric shapes, use related tools. The Concrete Arch Calculator handles circular arch rings, and the Concrete Cone Calculator handles cones and frustums.
Thickness has a direct effect on cubic yards. A 5-inch slab contains 25% more concrete than a 4-inch slab of the same area. That makes thickness one of the most important values in the calculator.
Do not allow the quantity calculator to choose thickness by project label. A “driveway” can serve passenger vehicles, delivery trucks or other loads. A “patio” can be ground-supported or part of a more complex structure. Enter the thickness shown on approved plans or required by the project.
If a pour includes multiple thicknesses, keep them separate. This improves both material accuracy and communication with the crew.
New Hampshire’s climate makes seasonal placement planning especially important. Concrete quantity itself is still calculated from geometry, but cold weather can affect scheduling, subgrade condition, protection and curing. Frozen ground should not be treated as a stable prepared base, and the placement team should follow the project specification and appropriate cold-weather concrete practices when temperatures are low.
Footing depth and frost protection are design and code questions rather than calculator defaults. Do not enter a deeper footing simply because “New Hampshire is cold” without the approved detail. For material estimating, use the actual footing depth shown by the applicable design or prescriptive requirement.
Winter access can also change delivery logistics. Snow storage, narrow drives, soft shoulders and steep grades can affect mixer-truck access even when the concrete volume is modest. Confirm access before scheduling delivery.
Spring projects can encounter saturated soils and soft base conditions after snowmelt. Summer brings more favorable temperatures but can still require planning for rapid evaporation, wind and curing. Fall work may be comfortable for placement while nights become colder. Winter placements can require heated materials, insulation, enclosures or other protective measures depending on the specification and conditions.
The calculator does not alter cubic yards based on season because the physical volume of the concrete shape does not change. Instead, seasonal conditions should be reflected in logistics, labor, protection, scheduling and contingency planning.
A volume calculation assumes the concrete depth is reasonably consistent. Poorly graded base creates low spots that consume extra concrete and high spots that reduce slab thickness. Verify the prepared base before finalizing the order.
Drainage can also influence slab elevation and grading. Surface slope usually does not change quantity much when thickness is consistent, but wedges, ramps, transitions and depressed drain zones can. Measure those areas from the actual detail.
On sloped or retaining situations, concrete quantity is only part of the problem. Stability, foundation design, drainage and structural requirements may require professional evaluation.
Reinforcement should be estimated from approved details rather than inferred from concrete square footage. Rebar size, spacing, cover, lap length and supports can vary significantly by slab, footing, wall or other structural element.
Once reinforcement is known, use the Concrete Rebar Calculator for bar quantity. Keeping reinforcement and concrete volume as separate calculations makes it easier to revise the project if the geometry or bar layout changes.
Volume tells you how much concrete is required, not what mixture should be supplied. Specified compressive strength, exposure, aggregate, slump, air content, admixtures and water-cement ratio are separate requirements.
For ready-mix structural work, provide the supplier with the required mixture specification. For small non-structural batch planning, the Concrete Mix Ratio Calculator can compare component proportions, but a nominal ratio should not replace an approved structural mixture.
New Hampshire does not have one municipal driveway-permit process that applies identically in every town and city. Local governments can administer building permits and may have zoning, public works, highway, excavation or driveway-access requirements. State-maintained roads can involve separate transportation requirements from locally maintained streets.
For a driveway, sidewalk, curb, retaining structure or concrete work near a road, identify who owns or maintains the right-of-way first. Then check the applicable municipal building, planning, public works or highway office. Material quantity should be calculated from the approved dimensions after access width, drainage, slope and right-of-way conditions are resolved.
The statewide code statute makes clear that local laws, land-use restrictions, dimensional limits and other applicable requirements continue to matter alongside the state building code. That is why this page separates concrete arithmetic from permit interpretation.
Concrete associated with public roads, drainage, sidewalks, culverts, bridge approaches or municipal infrastructure should be estimated from the approved civil or public-works drawings. Quantity formulas remain the same, but dimensions, reinforcement, concrete mixture, testing, traffic control and inspection requirements can be project specific.
For private work that touches a public right-of-way, do not assume the property-side concrete dimensions are the same as the permitted road or sidewalk detail. Use the final approved geometry for the material order and keep public-work quantities separate from private flatwork where practical.
Before scheduling concrete, verify the forms, reinforcement, embedded items, access, crew, finishing equipment and curing method. On wooded, rural, steep or tight residential sites, truck access and staging can be a major part of the plan. A pump, buggy or long chute may be needed even when the concrete volume itself is straightforward.
Check weather near pour day and plan for sun, wind or rain conditions that could affect placement and finishing. If rain is possible, use the Concrete Rain Pour Calculator as a planning aid.
If concrete must be placed near pedestrian or vehicle traffic, verify whether traffic-control or encroachment requirements apply to the operation.
Suppose a backyard slab is 18 ft × 14 ft at 4 inches thick. Surface area is 252 ft². Multiply by 4 ÷ 12 and the exact concrete volume is 84 ft³. Divide by 27 and the result is approximately 3.11 yd³.
A 10% allowance raises the planning quantity to about 3.42 yd³. If the chosen bagged product yields 0.60 ft³ per bag, that quantity represents about 154 bags. For a project of that size, it is worth comparing bag labor with a ready-mix quote.
Assume a private driveway is 35 ft × 12 ft at 4 inches thick and the approach area is 5 ft × 16 ft at 5 inches thick. The main slab contains approximately 5.19 yd³ and the apron contains approximately 1.23 yd³. Combined exact volume is about 6.42 yd³.
At a 10% allowance, the calculator returns approximately 7.06 yd³. Enter a current New Hampshire supplier price per cubic yard to produce a simple material estimate. If the apron or driveway work reaches a public right-of-way, review the applicable town, city or road-authority process separately.
The excavation can be wider or deeper than the finished concrete. Use the actual concrete shape.
Four inches is 0.333 ft, not 0.4 ft. The calculator handles the conversion automatically.
A driveway approach can add substantial volume, especially when it is thicker than the main slab.
Use a current supplier quote instead of relying on an old local price article.
Building-permit exemptions do not automatically remove zoning, transportation or public-right-of-way requirements.
Calculate different depths separately.
Recheck dimensions after forms and base preparation whenever possible.
When an existing slab or driveway is being replaced, estimate the new concrete from the finished replacement dimensions rather than the volume of demolished debris. Broken concrete expands into irregular pieces, so demolition haul-off volume is a different calculation from the compact volume of the new pour. A 4-inch slab removed from the site does not occupy the same loose volume in a truck or debris box that it occupied as a solid slab.
For replacement work, measure the area after deciding whether the new slab will match the old footprint. Repairs to settlement, drainage or alignment can change the finished dimensions. If the replacement includes a new thickened edge, widened parking area or revised driveway approach, calculate each new component separately.
Existing demolition can also reveal base problems that were not visible during the initial estimate. Soft zones, abandoned utility trenches or deep patches may require correction before forms are reset. Recheck the concrete depth after base repairs instead of ordering only from the old slab thickness.
If the project is a localized patch instead of full replacement, use the Concrete Repair Calculator to estimate patch volume. Keeping repair work separate from full-depth replacement makes both the material estimate and project scope easier to understand.
A sloped site can make a simple-looking concrete project more difficult to measure. The most important quantity question is whether the concrete maintains a consistent thickness along the slope or forms a wedge with one edge deeper than the other. A uniformly thick slab can still be estimated from surface dimensions and thickness, while a true wedge requires average-depth or prism geometry.
For a rectangular wedge whose thickness changes uniformly from one edge to the opposite edge, a useful quantity method is to multiply plan area by the average of the two concrete depths. For example, if one side is 4 inches thick and the opposite side is 8 inches thick, the average depth is 6 inches when the change is linear across the slab. This method should only be used when the actual geometry really is a uniform wedge.
Convert the average depth to feet before multiplying by plan area.
Do not use extra concrete as a substitute for proper grading or retaining design. If a project on a slope needs retaining walls, grade beams, stepped footings or engineered support, calculate those structural components from their approved dimensions. The general Concrete Wall Calculator and Concrete Strip Calculator can help with material quantity after the structural geometry is known.
Two ready-mix quotes can look different even when the headline price per cubic yard is similar. Before comparing totals, confirm that each quote refers to the same concrete mixture, order quantity and delivery assumptions. A lower cubic-yard price may be offset by short-load fees, fuel surcharges, minimum quantities or additional charges for waiting time and special placement conditions.
Use the calculator to create one consistent order quantity first. Then ask each supplier to price that same quantity and specified mix. This gives you a cleaner comparison than using a different rounded quantity for every quote. If the supplier requires ordering in a particular increment, update the final purchase quantity after the mathematical estimate is complete.
Also consider placement logistics. A supplier quote for concrete delivered to the curb is not the same as an installed price at forms behind a building or down a steep access path. Pumping, buggies, extra labor or traffic-control needs can be separate from the ready-mix invoice. The calculator’s cost output is intentionally limited to concrete material so those project-specific items remain visible instead of being hidden inside an unexplained rate.
For current statewide code and permit rules, use the New Hampshire General Court’s official RSA 155-A text. The statute defines the current state building code, explains local enforcement mechanisms and addresses building permits. For broader residential concrete construction practice, the American Concrete Institute publishes ACI PRC-332.1-18 Guide to Residential Concrete Construction.
Measure each finished concrete shape separately, then combine the exact volumes before adding your selected ordering allowance.
Common questions about concrete yards, bags, driveway quantities, cost and New Hampshire project planning.