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Free Construction Calculator Hub

15 tools covering concrete, structural, earthwork, aggregates, and site drainage — all in one place, always free.

Home / Construction Calculator
Concrete & Structural
Earthwork & Aggregates
Site Development & Drainage
Concrete Slab Details
ft
ft
in
%

Enter your slab dimensions to see how much concrete you need.

Slab-on-Grade Package
ft
ft
in
in
%

Enter your slab dimensions to see the full material package: concrete, mesh, vapor barrier, and base rock.

Foundation Wall Details
ft
ft
in
%

Enter your wall dimensions to see concrete volume needed.

Footing Details
ft
in
in
%

Enter your footing dimensions to see concrete and rebar needed.

Asphalt Area Details
ft
ft
in
lb/ft³
Typical hot-mix asphalt runs 140–150 lb/ft³

Enter your paved area dimensions to see tons of asphalt needed.

Gravel Coverage Details
ft
ft
in
tons/yd³
Typical gravel runs 1.35–1.45 tons per cubic yard

Enter your coverage area to see how much gravel you need.

Base Rock Details
ft
ft
in
%
Base rock compacts down, so you order more loose material than the final depth
tons/yd³

Enter your area and compacted depth to see loose base rock needed.

Fill Dirt Details
ft
ft
ft
%
tons/yd³

Enter your area and fill depth to see how much dirt you need.

Aggregate Material Details
ft
ft
in
tons/yd³
%

Pick a material and enter your coverage area to see tons needed.

Compaction Conversion
yd³
%
How much more loose material is needed than the final compacted result — typically 15% for base rock/fill, 20-30% for clay soils

Enter a known volume and compaction factor to convert.

Rip Rap Details
ft
ft
in
tons/yd³

Pick a rock class and enter your coverage area to see tons needed.

Excavation Details
ft
ft
ft
%
Excavated soil takes up more space than it did in the ground — typically 20–30% more
yd³

Enter your dig dimensions to see volume and truck loads needed.

Rebar Grid Details
ft
ft
in
%

Enter your slab dimensions and spacing to see total rebar needed.

Retaining Wall Details
ft
ft
in
in
%
in
ft

Enter your wall dimensions to see blocks and base gravel needed.

Pipe Bedding Details
ft
in
in
in
in
tons/yd³

Enter your trench and pipe dimensions to see bedding material needed.

Concrete volume formula

Cubic Yards = (Length × Width × Thickness ÷ 12) ÷ 27

Always add 5–10% for waste, spillage, and uneven subgrade. Ready-mix is typically ordered by the cubic yard; bagged concrete is calculated in cubic feet, where one 60 lb bag yields about 0.45 cubic feet.

Why base rock and gravel need a compaction allowance

Loose material compacts down once it's spread and rolled or tamped. If you need a 4" compacted base, you typically need to order 15–20% more material by volume than the final depth, since compaction reduces the loose volume.

Bank volume vs. swelled volume in excavation

Soil in the ground (bank measure) takes up less space than the same soil once it's dug up and loosened (swelled measure). This is why the dirt from a hole never fits back into the hole it came from — always estimate hauling based on the swelled volume, not the bank volume.

Rebar spacing and grid layout

Rebar is typically placed in a grid pattern at a set spacing (commonly 12" or 18" on-center for slabs) running in both directions. Total linear footage combines both directions, and a waste allowance accounts for overlaps at splices and trimming at edges.

Why use this construction calculator?

Instant Results

Updates in real time as you type — no need to hit calculate.

15 Tools in One

From concrete and rebar to pipe bedding and retaining walls — everything grouped by category.

100% Private

All calculations run in your browser. Your numbers are never stored or sent anywhere.

Works on the Job Site

Fully responsive — pull it up on your phone right at the site.

Frequently Asked Questions

How much extra concrete should I order?
Most contractors add 5–10% over the calculated volume to account for spillage, subgrade irregularities, and minor form deviations. For complex pours or uneven ground, some go as high as 15%.
Why do gravel and base rock calculations differ?
Gravel used for drainage or decorative coverage is typically ordered at its loose, uncompacted volume. Base rock used under slabs, driveways, or pavers is compacted after placement, so you need extra loose material upfront to reach your target compacted depth.
How is excavation volume different from the finished hole size?
The hole itself is measured at "bank" volume — the soil's size while still in the ground. Once removed, that same soil expands (swells) due to added air pockets, typically by 20–30%. Hauling and disposal costs should be based on the swelled volume, not the bank volume.
Is this construction calculator free?
Yes — completely free, forever. No account required, no premium tier.
What's the difference between the Aggregate and Gravel calculators?
The Gravel calculator is a quick single-purpose tool with a typical gravel density pre-set. The Aggregate calculator is more flexible — pick from several common materials (crushed stone, sand, pea gravel, crushed concrete, decomposed granite, river rock) and it auto-fills the right density, or you can enter your own for a specific product.