Know exactly how much to order.
Free material calculators, formula shown. Try one right here.
Drywall Calculator
Each door deducts 21 sq ft.
Each window deducts 12 sq ft.
Full drywall calculator with the formula and a worked example →
All 10 calculators
Pick your material
Interior & Finishing
Everything inside the walls once the structure is up.
Structural
Walls, framing, insulation and anything that carries load.
Landscaping & Groundwork
Beds, paths, driveways and bulk material by the yard.
No calculator matches that yet. More are being added every week.
How the numbers are worked out
Quantities you can check, not just trust
By BuildTallyFormulas published on every calculator page
The coverage figures behind each calculator come from published manufacturer specifications and standard trade practice — not from other calculators. Every calculator is checked by hand against its own worked example before it goes live, and the full formula sits on its page so you can follow each step.
Where the trade disagrees with itself, the page says so instead of picking a side silently. If a number looks wrong, tell us — it gets checked against the source and corrected. More on this on the about page.
Reading the result
Square footage is not an order
Area tells you how much surface there is. A supplier sells sheets, rolls, bags and cubic yards. Getting from one to the other takes three steps, and every calculator here does all three:
- Measure the net area — walls, floor or bed, minus doors and windows.
- Add a waste allowance for cuts, breakage and offcuts you cannot reuse.
- Round up to whole units — the sheet, roll or bag you actually carry out of the store.
Some materials need more than that. Concrete block is counted on its nominal size, which includes the mortar joint. Wallpaper is counted strip by strip, because a pattern repeat wastes paper at the top of every drop.
Not sure how much extra to allow? The waste factor guide covers typical allowances material by material.
| Material | Area ÷ coverage | BuildTally |
|---|---|---|
| Wallpaper | Wall area ÷ roll area. Ignores the pattern repeat — can leave you a roll short. | Strips per roll after the repeat, then rolls. Same room: 8 rolls instead of 7. |
| Concrete block | Measured block size — about 7.5% more blocks than the wall takes. | Nominal size with the mortar joint: 1.125 blocks per sq ft of face. |
| Drywall | Sheets only. | Sheets after door and window deductions, plus compound, tape and screws. |
Questions
Frequently asked
Why is the result higher than my square footage divided by coverage?
Because you cannot buy part of a sheet, roll or bag. Each calculator adds a waste allowance for cuts and breakage, then rounds up to whole units the way a supplier sells them. Wallpaper goes further and counts strip by strip against the pattern repeat, which is why it can come out a full roll higher than the area method.
What waste factor should I use?
Each calculator starts with the allowance typical for that material: 10% for drywall and tile, 5% for concrete block, 15% for lumber. Go higher for diagonal tile layouts, rooms with many corners or your first project. The waste factor guide explains when to change it.
Can I use metric measurements?
Yes. Switch between ft / in and m / cm at the top of any calculator. The results convert with it, and your choice is remembered on this device for the other calculators.
How accurate are the results?
They are planning estimates built on published manufacturer figures and standard trade practice, and every calculator is checked against its own worked example. Real jobs vary with layout and installation method, so confirm large orders with your supplier or contractor.
Is anything I type saved or sent anywhere?
No. The calculators run entirely in your browser. Nothing you enter is sent to a server or stored, apart from your ft / m preference, which stays on your device.
The calculator I need is not here. Will you add it?
Probably — decks, fences and siding are next. Email the material and what you are trying to work out, and it goes on the list.
Corrections
Found a number that looks wrong?
Send the calculator, the inputs you used and what you expected. It gets checked against the source figures, and the page is corrected if it turns out to be wrong.
Email lengche2222@gmail.com