BuildKit

Free calculators for home projects — know what to buy before you go to the store.

Measure twice, buy once.

Ten free calculators for the projects real people actually do — a room to paint, a slab to pour, a deck to build. Punch in your measurements and get a straight answer: how much to buy, in the units the store sells it in. No sign-up, no fuss, everything figures right here in your browser.

10 project calculators
Feet, inches & gallons
Waste allowance built in
Copy a shopping summary

Pick your project

Tap a card to jump straight to that calculator.

TOOL 01 Paint Calculator

Tell it the size of the room and it works out how much wall you really have — after doors and windows come off — then turns that into gallons of paint (and primer, if the walls need it).

Room length (ft) Room width (ft) Wall height (ft) DoorsEach door counts as 21 sq ft WindowsEach window counts as 15 sq ft Coats of paint Coverage (sq ft per gallon)Most paints cover about 350 Waste allowance (%)For spills, touch-ups, and thirsty walls Price per gallon ($)Optional — for a cost estimate Paint the ceiling too Add a coat of primer

Your paint list

Copied — take it to the store.

TOOL 02 Concrete Calculator

Pick the shape of your pour and enter the size. You get the volume in cubic yards for a ready-mix truck, plus how many bags of mix it takes if you would rather do it yourself.

Shape Waste margin (%)10% is a safe bet for most pours

Length (ft) Width (ft) Thickness (in)4 in is standard for patios and walks

Your concrete list

Copied — take it to the store.

TOOL 03 Flooring Calculator

For laminate, vinyl plank, engineered wood, and solid hardwood sold by the box. Measure the room (or type in the total area) and it tells you how many boxes to put in the cart.

Measure by Coverage per box (sq ft)Printed on the box — often 20–24 Waste allowance (%)10% covers cuts; 15% for diagonal layouts Price per box ($)Optional — for a cost estimate

Room length (ft) Room width (ft)

Your flooring list

Copied — take it to the store.

TOOL 04 Tile Calculator

Floors, showers, and backsplashes. Choose a tile size, and it counts the tiles and boxes you need, plus bags of thinset to set them with.

Area length (ft) Area width (ft) Tile size Tiles per box Waste allowance (%)10% straight lay, 15% diagonal or patterned

Your tile list

Copied — take it to the store.

TOOL 05 Drywall Calculator

Finishing a room or a basement? Enter the room size and get the sheet count, a screw estimate, and how many buckets of joint compound the job will eat.

Room length (ft) Room width (ft) Wall height (ft) Sheet size Waste allowance (%)For cuts around doors, windows, and outlets Include the ceiling

Your drywall list

Copied — take it to the store.

TOOL 06 Mulch & Soil Calculator

Garden beds eat more mulch than anyone expects. Enter the bed size and how deep you want it, and see the job in bulk cubic yards and in 2-cubic-foot bags, side by side.

Bed length (ft) Bed width (ft) Depth Bulk price ($ per cubic yard)Optional — for a cost estimate Bag price ($ per 2 cu ft bag)Optional — for a cost estimate

Your mulch & soil list

Copied — take it to the store.

TOOL 07 Fence Calculator

For a classic wood privacy fence with posts every 8 feet. Give it the run length and your picket size, and it counts posts, pickets, rails, and the concrete to set the posts.

Fence length (ft) Picket width (in)A standard picket is 5.5 in wide Gap between pickets (in)0 for a tight privacy fence

Your fence list

Copied — take it to the store.

TOOL 08 Deck Calculator

Boards run along the length of the deck, joists sit 16 inches apart underneath. Enter the footprint and board width, and get boards, joists, and a screw count that will not leave you short on a Sunday afternoon.

Deck length (ft)The direction the boards run Deck width (ft) Deck board width Waste allowance (%)For cuts, ends, and the odd bad board

Your deck list

Copied — take it to the store.

TOOL 09 Roofing Shingle Calculator

Shingles are sold by the square — 100 square feet — and three bundles make a square. Enter the roof size (or the house footprint plus its pitch) and get bundles, ridge cap, and underlayment rolls.

Roof length (ft)Along the ridge — also your ridge cap length Roof width (ft)One slope, eave to ridge — or footprint width with a pitch below Roof pitch Waste allowance (%)10% is standard; 15% for cut-up roofs

Your roofing list

Copied — take it to the store.

TOOL 10 Lumber / Board-Feet Calculator

Hardwood is priced by the board foot, not by the piece. Enter the size of your boards and how many you need, and it converts everything to board feet, linear feet, and dollars.

Thickness (in)A 2× board is 2 in thick (nominal) Width (in) Length (ft) Number of pieces Price per board foot ($)Optional — for a cost estimate

Your lumber list

Copied — take it to the store.

How to use these calculators

Measure the real space. A tape measure and five minutes beat guessing from the doorway. Round each measurement up to the nearest inch.
Type your numbers in. Results update as you type — no button to press. Leave the price boxes empty if you only want quantities.
Keep the waste allowance. Every calculator adds a little extra for cuts, mistakes, and the board with the ugly knot. It is cheaper than a second trip.
Copy the list. Hit “Copy results” and paste the summary into your phone's notes — that is your shopping list, quantities and all.

Questions people ask

How accurate are these estimates?

Close enough to shop with confidence — they use the same coverage figures printed on paint cans, concrete bags, and flooring boxes. Real rooms have crooked corners, thirsty drywall, and the occasional whoops, which is exactly why every calculator includes a waste allowance. If your number lands right on the edge between two quantities, buy the extra one; unused material in its packaging can almost always go back.

Why add a waste allowance at all?

Because almost nothing gets used at 100%. Flooring gets cut at every wall, tile breaks, concrete sticks to the wheelbarrow, and paint stays in the roller. Ten percent is a sensible default for straightforward jobs; bump it to 15% for diagonal tile or flooring, roofs with lots of valleys, or any project where the pattern has to match.

Bags of concrete mix or a ready-mix truck — which should I get?

Under about 1 cubic yard, bags are usually cheaper and can be mixed a few at a time at your own pace. Above that, the bag count (and the mixing) gets heavy fast, and a ready-mix truck wins on both effort and consistency. The concrete calculator shows both numbers so you can compare: if the bag count makes your arms tired just reading it, call the truck.

What exactly is a board foot?

A board foot is a measure of wood volume: a piece 12 inches wide, 12 inches long, and 1 inch thick — 144 cubic inches of wood. Lumberyards price hardwood this way because boards come in random widths and lengths. The formula is thickness (in) × width (in) × length (ft) ÷ 12, and the lumber calculator above does it per piece and for the whole stack.

Do I need an account, or does this cost anything?

No account, no cost, nothing to install. Every calculation happens in your own browser the moment you type — your measurements never leave your device, and the answers are yours to copy and take to the store.

About BuildKit

BuildKit started with a familiar scene: standing in a store aisle, phone in hand, trying to remember whether a 12-by-10 room takes two gallons of paint or three. These ten calculators answer the questions homeowners actually ask at that moment — how much paint, concrete, flooring, tile, drywall, mulch, fencing, decking, shingles, and lumber a project really needs.

Everything is in the units American stores sell: feet and inches, gallons, cubic yards, 40/60/80 lb bags, boxes, bundles, and board feet. Simple on purpose — measure, type, copy the list, and get the project done.