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EstimatorKit

Free construction calculator

Work out how much material you need — in bags, yards and tons

Give an area and a depth and this returns the quantity a supplier can act on: cubic yards, whole bags, tons on the scale ticket. Measurements go in the way they came off the tape, fractions and all, and the two numbers that quietly ruin orders are shown instead of hidden — the waste you are allowing for, and the extra depth that loose material needs because it compacts. Add what your yard charges per bag and per cubic yard and it also answers the real question, which is whether to carry bags home or pay for a delivery.

  • 100% free
  • No signup
  • Feet, inches and fractions
  • Bags, yards and tons
  • Your prices, not ours
Material

4 in is the usual slab for a patio, shed or walkway.

Shape

Feet unless you say otherwise. 12' 6 3/8", 150 in and 3.8 m all read correctly.

Add your prices to compare bags against bulk

We do not ship a price list — it would be wrong in half the country the day it shipped. These are yours.

Order this much concrete

3.11 cu yd

80 lb bags
140
Area
240 sq ft
Cubic feet
84

Bags or bulk

At 3.11 yd³ this is usually past the point where bags pay — that is 140 bags to carry and mix. Enter your own prices to compare properly.

All 66 calculators

Concrete and masonry, aggregates, framing and lumber, roofing, interior finishes, the yard and the pool, cost estimates and the reference charts — every one of them runs in this tab and answers in units a supplier sells.

Area & volume

10 tools

How to estimate materials for a job

Three steps, and the middle one is where most estimates go wrong.

  1. Measure the area the way you would write it down

    Type the length and width as they came off the tape — 12' 6 3/8" is a valid entry, and so are 150 in, 12.53 and 3.8 m. There is no decimal-feet conversion to do in your head first, which is the step that puts an error into an estimate before any arithmetic happens. For a round pad or a footing, switch the shape to circle and give the diameter instead.

  2. Set the finished depth, not the ordered depth

    Give the depth you want when the job is done: four inches of driveway base, three inches of mulch, one inch of paver sand. Where the material settles or compacts, the calculator orders deeper than that on purpose and tells you by how much — loose aggregate loses roughly a fifth of its depth under a plate compactor, which is why a four-inch order finishes at three and a bit.

  3. Read the order, then add your own prices

    The result is a quantity you can hand over: cubic yards, whole bags and tons. Open the price panel and enter what your supplier charges per bag, per yard and for delivery, and the page works out which way is cheaper for this specific job — including the short-load fee that makes small deliveries expensive and the minimum order that makes them expensive again.

Technical specifications

Calculators66 pages, from concrete and gravel to drywall, roofing and pool salt
Measurement inputFeet-inches-fractions (12' 6 3/8"), decimal feet, inches, yards, meters, centimeters, millimeters
Output unitsCubic yards and cubic feet, whole bags, short tons, squares, sheets, boxes and pallets
Waste allowanceShown separately from the bare quantity and adjustable on every page
Compaction and settlingApplied only to materials that lose depth, at a stated rate per material
PricesEntered by you — the site ships no price list and no regional averages
Coverage constantsEach marked fixed or variable, with the source and what moves it
Data keptNone — every calculation runs in this tab and nothing is uploaded

Frequently asked questions

How many bags of concrete are in a cubic yard?

Forty-five 80 lb bags, sixty 60 lb bags or ninety 40 lb bags. A cubic yard is 27 cubic feet and an 80 lb bag yields 0.6 of a cubic foot, so the arithmetic is 27 ÷ 0.6. That number is also the reason the site flags roughly a yard as the point where bags stop making sense: forty-five bags is 3,600 lb to lift twice and about two hours of mixing, which usually costs more than a short-load fee.

Why does the calculator order more material than my measurements say?

Two separate allowances, and both are shown rather than folded in. The waste allowance covers cuts and spillage and you set it. The compaction or settling allowance applies only to materials that lose depth after they are placed — gravel and crushed stone under a plate compactor, topsoil and compost after watering in. Set the waste to zero if you want the bare geometry; the compaction figure is per material and is explained on the page that uses it.

Do you sell materials or pass my details to someone who does?

No. There is no quote form, no lead capture and no partner supplier. That is worth stating because most calculators at the top of these searches belong to somebody who does sell the material, which is a fine reason to publish a calculator and also a reason their default quantities tend to round upward.

Where do the coverage numbers come from?

Each one is marked as either fixed or variable. Fixed numbers are definitional or manufactured — a roofing square is 100 square feet, a 4 × 8 sheet is 32 square feet, an 80 lb bag yields 0.6 cubic feet. Variable numbers are things like the weight of a cubic yard of topsoil, which genuinely changes with moisture and screening; those appear as editable defaults with a note saying what moves them, and your supplier's own figure should replace ours.

Can I enter metric measurements?

Yes — write the unit and it is read: 3.8 m, 380 cm, 3820 mm. The results still come back in yards, tons and bags, because that is what the suppliers behind roughly seventy percent of these searches sell in. A full metric output is not built yet.

Is this accurate enough to order from?

For quantities, yes: the geometry is exact and the coverage figures are the trade's own. What it cannot know is your site — a slab poured on soft ground takes more concrete than its dimensions say, and a delivery that has to be barrowed round the back changes what is worth ordering. Treat the number as the order and the site conditions as your judgement call.

About estimating materials from measurements

Every material estimate is the same three-step calculation wearing different clothes: work out an area, multiply it by a depth to get a volume, then convert that volume into whatever the supplier actually sells. The last step is the one that matters and the one most calculators skip. Nobody buys 1.48 cubic yards of concrete. They buy sixty-seven 80 lb bags, or they buy two yards from a truck and accept that half a yard goes into a form they will build for the purpose. A page that stops at the volume has handed you an intermediate result and called it an answer.

Two adjustments sit between the geometry and the order, and they pull in opposite directions. Waste is material you buy and do not place — offcuts, spillage, the tile that cracks. Compaction and settling are the reverse: material you place and then lose, because loose aggregate under a plate compactor gives up roughly a fifth of its depth and screened topsoil settles once it is watered in. Ignore the first and you make a second trip; ignore the second and the finished job is thinner than it was meant to be. Both are visible on every page here, with the bare figure next to the adjusted one, because a calculator that silently pads its own answer is not one you can check against a quote.

The unit conversions themselves are worth having open in their own right — the cubic yard calculator for turning an area and a depth into a delivery, and the square footage calculator for the rooms and lots that are never a plain rectangle. From there the material pages each add the part that is theirs: bag yields and the truck threshold on concrete, loose density and tonnage on gravel, and depth limits that are horticultural rather than structural on mulch.

What happens to the measurements you enter

Every number on this page is worked out by JavaScript running in the tab you are reading it in. Nothing you type — measurements, quantities, the prices your supplier quoted you — is uploaded, logged or kept, which is also why the calculators carry on working on a site with no signal.

Prices are the clearest case. When you enter what your supplier charges, that number is multiplied in the tab and then forgotten on reload — it is not sent anywhere, and there is no quote form here for it to feed.