Concrete Calculator Online
Figure out how much concrete a job needs — live results in cubic yards, cubic feet, cubic meters, and ready-mix bag counts, with per-field units, a waste allowance, and a shareable link. No ads, no sign-up.
Slab
Patios, driveways, sidewalks, and floor slabs.
⬓Footing
Strip footings, spot/pad footings, and foundations.
○Column
Round or square columns, piers, and post footings.
▯Wall
Foundation walls, retaining walls, and poured walls.
▤Stairs
Concrete steps, porch stairs, and landings.
⌐Curb & Gutter
Curb, gutter, and combined curb-and-gutter runs.
Also see the dedicatedFence Post Concrete Calculatorand Concrete Step Calculator.
Every unit, live
Cubic yards, cubic feet, cubic meters, and bag counts all update together as you type — no separate "calculate" step, no picking one unit for the whole form.
Built-in waste allowance
A default 10% overage is applied automatically and shown separately from the exact volume, so the number you order with already accounts for spillage and uneven subgrade.
Multi-item job totals
Pouring more than one slab, footing, or post? Add each one to a running list and get one grand total for the whole job.
A concrete calculator online built for how real projects are actually shaped
Most tools called a "concrete calculator" really only handle one shape — a flat slab — and expect you to force everything else into that box. Real Concrete Calculator is a free concrete calculator online that instead ships with a dedicated calculator for every common pour: slabs, footings, columns and fence posts, walls, stairs, and curb & gutter runs. Pick the shape that matches your project, enter your dimensions, and watch the numbers update as you type — no "Calculate" button, no page reload, no picking a single unit for the whole form.
Cubic yards, cubic feet, cubic meters — all at once
Concrete is bought by the cubic yard in the US, quoted in cubic feet for small DIY jobs, and measured in cubic meters almost everywhere else. Rather than making you pick one and convert by hand, every calculator here works as a combined concrete yard calculator, cubic yard calculator, and concrete calculator in cubic feet at the same time — the results panel shows cubic yards, cubic feet, and cubic meters together, live, next to a bag count and an estimated weight. If you already know your project's square footage, you can plug that straight in as one of the two footprint dimensions, which effectively makes this a concrete calculator by square foot as well — no separate tool required.
One concrete material calculator for slabs, footings, walls, and more
The Slab Calculator doubles as aconcrete slab thickness calculator — enter length, width, and thickness for a patio, driveway, or floor slab, and it shows the standard thickness ranges builders actually use alongside your result. Need footings under a wall or a deck? TheConcrete Footing Calculator handles both continuous strip footings and individual spot/pad footings. Pouring a foundation or retaining wall? The Concrete Wall Calculatorcovers that, and the Column Calculator switches between round and square columns for piers and posts. Setting an actual fence line takes it a step further — the dedicatedFence Post Concrete Calculator is built specifically around post-hole diameter and depth, with an "add to job list" total for every post on the run. And for a short flight of steps up to a porch or patio, theConcrete Step Calculator — also available from the main Stairs page — works from rise, run, and step count instead of forcing stair geometry into a slab formula.
Ready-mix or bagged? This concrete mix calculator shows both
Every result includes bag counts for common 40, 60, and 80 lb bags (or 20, 25, and 40 kg bags on the metric toggle), so this doubles as a ready mix concrete calculator and aconcrete mix calculator at the same time — you can compare bagged mix against a ready-mix truck order without switching tools. As a rough guide, bagged mix tends to make sense up to roughly 1–1.5 cubic yards; beyond that, a ready-mix delivery is usually cheaper and faster per yard. Add an optional price per cubic yard in the "Order options" section and the results panel turns that volume into an estimated total cost, so you can sanity-check a supplier's quote before you commit.
Built-in waste allowance, weight, and a shareable result
Concrete work almost always uses more material than the pure geometry suggests — uneven subgrade, form leakage, and ordinary spillage all add up. Rather than a footnote telling you to "add some extra," every calculator applies an adjustable waste percentage (10% by default) directly to the volume, and shows the exact geometric figure and the recommended order side by side so you can see exactly what the buffer adds. Each result also includes an estimated weight — handy if you're using this as a concrete slab weight calculator to check what a delivery truck, hand cart, or structural support needs to handle. Once you're happy with a result, the "Copy shareable link" button encodes your inputs into the URL, so you can send an exact calculation to a contractor or supplier instead of reading numbers over the phone.
Looking for the Home Depot concrete calculator?
If you searched for the Home Depot concrete calculator and ended up here, you're in the right place — the underlying math (length × width × thickness, converted to cubic yards) is the same one every hardware-store tool uses. The difference is coverage and detail: this site adds dedicated calculators for footings, columns, fence posts, walls, stairs, and curb & gutter runs, all with live results, a waste allowance, bag counts in two systems, and weight and cost estimates built in, rather than a single slab-only form.
Straightforward formulas, shown in the open
There's no hidden markup or black-box "estimate" here — every calculator uses the same formulas a contractor would use by hand: length × width × thickness for slabs, footings, and walls; π × radius² × height for round columns and post holes; and a stacked-step approximation for stairs. The How we calculate page walks through exactly how volume, waste percentage, and bag yields are derived, so you can see where every number in the results panel comes from. Whether you think of this as a concrete yards calculator, a concrete calculator online, or just the tool you use before calling a supplier, the math underneath is the same and it's yours to check.
Frequently asked questions
How do I calculate how much concrete I need?+
Multiply the length, width, and thickness (or height) of your project — all converted to the same unit — to get volume, then convert to cubic yards or cubic feet. Pick a shape above, enter your dimensions, and this calculator does that conversion automatically, live, with a waste allowance built in.
How do I calculate how much concrete I need for a slab?+
For a slab, multiply length × width × thickness. A 10×10 ft slab at 4 in. thick works out to 10 × 10 × (4/12) = 33.3 cubic feet, or about 1.23 cubic yards. The Slab Concrete Calculator above gives you this instantly, along with cubic meters, weight, and bag counts.
How much concrete do I need for a 10x10 slab?+
A 10×10 ft slab needs about 1.23 cubic yards (33.3 cubic feet) at a standard 4-inch thickness, or roughly 1.85 cubic yards at 6 inches for a driveway-grade slab. Enter your exact thickness in the Slab Calculator for a precise figure, including waste.
How many bags of concrete do I need for a slab?+
Divide your slab's volume by the yield of the bag size you're using — an 80 lb bag yields about 0.6 cubic feet. The Slab Calculator lists bag counts for 40, 60, and 80 lb bags automatically once you enter your dimensions, no separate math required.
How many 80 lb bags of concrete do I need for a 10x10 slab?+
A 10×10 ft slab at 4 inches thick needs about 62 bags of 80 lb concrete mix once a 10% waste allowance is included (roughly 36.7 cubic feet ÷ 0.6 cubic feet per bag). Adjust the thickness or waste % in the Slab Calculator to recalculate for your exact slab.
How many 60 lb bags of concrete do I need?+
Each 60 lb bag yields about 0.45 cubic feet of mixed concrete — divide your total cubic feet by 0.45 and round up. Or enter your dimensions above and the results panel shows the 60 lb bag count directly, no manual division needed.
How many bags of concrete are in a cubic yard?+
One cubic yard (27 cubic feet) takes about 90 bags of 40 lb mix, 60 bags of 60 lb mix, or 45 bags of 80 lb mix. Bag yield varies slightly by brand and mix design, so check the yield printed on your specific bag for an exact count on a large order.
How do I calculate concrete in cubic yards?+
Find your volume in cubic feet (length × width × thickness, all in feet), then divide by 27 — there are 27 cubic feet in a cubic yard. Every calculator on this site shows cubic yards automatically alongside cubic feet and cubic meters as you type.
How do I convert cubic feet of concrete to cubic yards?+
Divide cubic feet by 27. For example, 100 cubic feet ÷ 27 ≈ 3.7 cubic yards. The results panel on every calculator shows both units side by side, so you don't need to convert by hand.
How much concrete do I need for a footing?+
Multiply the footing's length × width × depth, the same way as a slab. A 20 ft run of footing that's 18 in. wide and 12 in. deep needs about 1.11 cubic yards. Use the Footing Calculator above for either strip (continuous) or spot/pad footings.
How much concrete do I need for a post hole?+
Post holes are calculated as a round column: π × radius² × depth. A typical 10-inch-diameter hole, 2 feet deep, needs about 0.04 cubic yards (roughly 1.1 cubic feet). The Fence Post Concrete Calculator lets you enter hole diameter and depth directly and totals multiple posts for a whole fence line.
How do I calculate concrete for a column?+
For a round column, use π × radius² × height; for a square or rectangular column, multiply side length × side length × height. The Column Calculator switches between round and square automatically and gives you the volume for one column or a whole set.
How much extra concrete should I order for waste?+
Add 5–10% on top of your exact calculated volume to cover spillage, uneven subgrade, and formwork loss — 10% is a safe default for most DIY pours. Every calculator here applies an adjustable waste percentage automatically and shows the "recommended order" figure separately from the exact geometric volume.
What is the standard thickness for a concrete slab?+
4 inches is standard for patios, walkways, and shed floors. Driveways typically use 5–6 inches, and areas that see heavy trucks go up to 6–8 inches. Enter your own thickness in the Slab Calculator — there's no single right answer for every project.
Should I buy concrete bags or order ready-mix concrete?+
Bagged mix generally makes sense up to about 1–1.5 cubic yards (roughly 45–70 bags) — beyond that, ready-mix concrete delivered by truck is usually faster and cheaper per yard. This calculator shows both bag counts and total cubic yards so you can compare either option before ordering.
How do I calculate concrete for a wall?+
Multiply the wall's length × height × thickness. An 8-inch-thick, 4-foot-tall wall running 20 feet needs about 2.17 cubic yards including a 10% waste allowance. Use the Wall Calculator above, and add the footing underneath separately with the Footing Calculator.
How much concrete do I need for steps?+
Stair volume is estimated as a stack of solid rectangular steps: 0.5 × rise × run × number of steps × width, plus any landing. The Stairs Calculator (or the dedicated Concrete Step Calculator) does this automatically — just enter your rise, run, step count, and width.
How much does concrete cost per cubic yard?+
Ready-mix concrete typically runs $125–$180 per cubic yard in the US, though prices vary by region, mix strength, and delivery minimums — always confirm with a local supplier. Enter a price per cubic yard in any calculator's "Order options" section for an instant cost estimate.
How much does a bag of concrete cover?+
An 80 lb bag covers about 0.6 cubic feet, a 60 lb bag about 0.45 cubic feet, and a 40 lb bag about 0.3 cubic feet once mixed — roughly a 2×2 ft area, 1.8 inches deep, per 80 lb bag. Switch the bag size selector in any results panel to compare coverage.
Can I calculate concrete in metric units?+
Yes — every input field has its own unit dropdown including meters and centimeters, and results always show cubic meters alongside cubic yards and cubic feet. Switch the bag calculator to "Metric (kg)" to see 20, 25, and 40 kg bag counts instead of US pounds.
Looking for the Home Depot concrete calculator?+
Home Depot's in-store calculator uses the same length × width × thickness math as every calculator on this page — ours just runs live as you type, covers more project shapes (footings, columns, walls, stairs, curbs), and shows bags, weight, and cost all at once without switching tools.