Construction Calculator
Calculate construction materials, areas, and volumes. Enter your measurements and get the quantities you need.
What are you calculating?
Select a highlighted project on the house or choose a calculator below.
Roofing Calculator
Coming next: the roof’s size and pitch in, squares and bundles of shingles out. Until then, pick another part of the house.
Free construction calculators by job
Each calculator opens with the example on its card worked out, a drawing to scale and a shopping list; type your own sizes over it.
Concrete
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Concrete Calculator
Ready-mix yards or bags for slabs, footings, walls, round columns and steps.
10 × 10 ft slab, 4 in thick 1.36 cu yd with 10% extra, or 62 bags of 80 lb
Area and volume
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Square Footage Calculator
Any room or lot shape, pieces added or cut out: square feet, yards, meters, acres and the flooring to buy.
L-shaped room, 15 ft 6 in × 12 ft plus 8 ft × 4 ft 6 in 222 sq ft buy 245 sq ft of flooring with 10% extra
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Cubic Yard Calculator
Soil, gravel or mulch for a bed, path or pad: the yards to order and the bags.
10 × 12 ft mulch bed, 3 in deep 1.22 cu yd with 10% extra: order 1.5 cu yd, or 17 bags of 2 cu ft
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Cubic Feet Calculator
A bed, box or room in cubic feet, yards, gallons and liters, and the bags to fill it.
4 × 8 ft raised bed, 12 in deep 32 cu ft = 239 US gallons; 16 bags of 2 cu ft
From tape to shopping list
Every calculator on BuilderMath is a material estimator for one part of a building job. It takes the sizes you measure, works out the material calculation and ends with a material list you can take to a store or a supplier. The steps are the same on each one.
Measure the way the tape reads
Type feet in the first box, inches in the second and the fraction of an inch from the list, exactly as the blade shows it. Nothing has to be turned into decimals by hand, and a size typed as “3-1/2” gets a one-tap fix.
Build the job from pieces
Pick a shape for each piece: rectangle, triangle, trapezoid, circle, half circle, ring, oval or border. Add a piece for an L-shaped room, take one away for a doorway, a hearth or a post. A drawing to scale follows the sizes as you type, with a numbered callout for each one, so a wrong size shows up as a wrong shape.
Read the total in the unit you order
Floors and lots come out in square feet, ready-mix, soil, gravel and mulch in cubic yards, bagged material and boxes in cubic feet. The line under the total gives the other units, metric included, and the worked steps under the plate show every multiplication.
Buy in store units
The shopping list rounds up to what is sold: whole bags, ready-mix by the quarter or half yard, flooring in whole square feet. The extra for cuts and waste sits on its own line, so you can see it and change it. Print the list, or save it as a PDF from the print dialog.
Adding feet, inches and fractions
Tape math is the part of construction math that goes wrong most often: feet run in twelves, inches in sixteenths, and a calculator that only knows decimals handles neither. Here is a job worked the way a carpenter does it on paper: Baseboard for two walls, less a doorway, 12′ 6 1/2″ + 9′ 3 3/4″ − 2′ 11 5/8″, step by step.
Turn each reading into inches
12′ 6 1/2″ = 12 × 12 + 6 1/2 = 150 1/2 in; 9′ 3 3/4″ = 9 × 12 + 3 3/4 = 111 3/4 in; 2′ 11 5/8″ (taken away) = 2 × 12 + 11 5/8 = 35 5/8 in.
Add, then take away
150 1/2 + 111 3/4 − 35 5/8 = 226 5/8 in. In sixteenths: 2,408 + 1,788 − 570 = 3,626, and 3,626 ÷ 16 = 226 remainder 10, so 226 10/16 = 226 5/8 in.
Back to feet and inches
226 5/8 ÷ 12 = 18 remainder 10 5/8, so 18′ 10 5/8″. As decimal feet: 226.625 ÷ 12 ≈ 18.8854 ft.
Into metric
226.625 × 25.4 = 5,756.275 mm = 575.6275 cm = 5.756275 m. Exact: an inch is 25.4 mm by definition, so a sixteenth is 1.5875 mm.
Total = readings added − readings taken away, each as feet × 12 + inches
150 1/2 + 111 3/4 − 35 5/8 = 226 5/8 in = 18′ 10 5/8″
Feet = inches ÷ 12; millimeters = inches × 25.4.
Carrying sixteenths and inches
Add the fractions as sixteenths first. Every sixteen sixteenths carry one inch, and every twelve inches carry one foot. Taking away is the same in reverse: when a column runs short, borrow an inch as sixteen sixteenths or a foot as twelve inches. Working everything in inches, as the steps above do, does the carrying for you.
This is the feet-inch-fraction math a handheld construction calculator does, here in the browser of the phone in your pocket. Multiplying and dividing lengths, a tape chart and decimal-to-fraction conversion belong to the feet and inches calculator with a sixteenth-inch tape chart.
Builder's units by definition
Construction measurement in the US runs on inches, feet and yards, with square and cubic units built from them. Each is defined exactly in metric, so a conversion never drifts: an inch is 25.4 mm, and a sixteenth of an inch is 1.5875 mm.
| Unit | In US units | Metric, exact | Used on |
|---|---|---|---|
| 1/16 in | 0.0625 in | 1.5875 mm | Tape readings on this page |
| 1 in | 1/12 ft | 25.4 mm | Every size you type |
| 1 ft | 12 in | 0.3048 m | Every size you type |
| 1 yd | 3 ft | 0.9144 m | Cubic yards |
| 1 sq ft | 144 sq in | 0.09290304 m² | Square footage |
| 1 sq yd | 9 sq ft | 0.83612736 m² | Flooring |
| 1 acre | 43,560 sq ft | 4,046.8564224 m² | Lots |
| 1 cu ft | 1,728 cu in | 28.316846592 L | Cubic feet, bags |
| 1 cu yd | 27 cu ft | 0.764554857984 m³ | Cubic yards, concrete |
| 1 US gal | 231 cu in | 3.785411784 L | Cubic feet |
Definitions from NIST Handbook 44 (2026), NIST Special Publication 811: 1 in is 25.4 mm exactly, and every metric figure here is that multiplied out, so none is rounded.
A cubic yard holds 27 cubic feet, which is why every volume calculator here divides cubic feet by that number before it orders ready-mix, gravel or soil. Area is the same idea one dimension down: a square foot is a foot by a foot, whatever the shape of the room.
Estimating a job: quantities, then costs
A construction estimate starts with quantities, not prices. Work out each material from the plans or your own measurements, add the extra for waste, and round up to what is sold. Only then put a price on it. A home building or remodeling estimate is the same list, done for every part of the house.
Materials, labor, overhead and margin
Materials are the quantity times the local unit price, from a current quote or a supplier's price list. Labor is the hours each task takes times the local hourly wage; the U.S. Bureau of Labor Statistics publishes wages for the construction trades by metro area in its Occupational Employment and Wage Statistics. A contractor's overhead and margin go on their own lines, so both sides of a bid can see them.
Prices and wages change with the ZIP code and the month, so this page gives the method and no prices. The quantities are the part that does not change: measured once and worked out here, they price the same job anywhere.
Construction calculator FAQ
What does a construction calculator do?
It turns the sizes you measure into lengths, areas and volumes, and those into what to buy. Pick the part of the building you are working on: the concrete calculator gives the yards and bags for a slab, a footing, a wall, a column or steps; the square footage calculator gives a floor's area and the flooring to buy; the cubic yard and cubic feet calculators give the mulch, gravel or soil for a bed or a planter. Each works from sizes in feet, inches and sixteenths, with a drawing to scale, the steps and a shopping list.
Is this construction calculator free?
Yes. These are free construction calculators: there is no account, no download and nothing to pay, and they work in a phone's browser. The sizes you type stay in your browser; the privacy policy says what the site keeps.
How do I add feet and inches with fractions?
Turn each length into inches (feet times 12, plus the inches), add them up with the fractions in sixteenths, then divide by 12 for feet and keep the remainder as inches. For example: 12′ 6 1/2″ + 9′ 3 3/4″ − 2′ 11 5/8″ = 18′ 10 5/8″.
Is there a construction calculator app?
You do not need one: the calculators run in the browser on a phone, a tablet or a computer, with nothing to install. Copy link keeps your sizes in the address, so a job opens again later or goes to someone else as a link.
How do I calculate the quantity of building materials?
Measure the area or the volume, divide by what one unit covers or holds (the maker's coverage or bag yield), add the extra for waste on its own line and round up to whole store units. Each calculator does this for one material and names the documents behind its figures. To keep the list as a PDF, print it and choose Save as PDF.
How do I estimate a construction job?
Quantities first, then prices: materials as quantity times the local unit price, labor as hours times the local wage (the Bureau of Labor Statistics publishes construction wages by area), then overhead and margin on their own lines.
How many cubic feet are in a cubic yard?
27, because a yard is three feet each way. The cubic yard calculator for soil, gravel or mulch does the division for any bed, path or pad.
What is 1/16 inch in decimals and millimeters?
0.0625 in, which is exactly 1.5875 mm, because an inch is defined as 25.4 mm.
Sources
The unit definitions on this page come from these documents, checked 9 November 2026. Each calculator names the sources of its own figures on its page.
- NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement
- NIST Special Publication 811, Guide for the Use of the International System of Units, 2008 edition
How BuilderMath calculates sets out the rules every figure follows; About BuilderMath says who runs the site and how to send a correction.