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Calculators

Calculators that round up right

Most calculators stop at a decimal and leave you to work out what to buy. These go to the shopping list: the exact amount, the amount with a waste allowance, and the whole boxes or bags to buy, always rounded up, with every number explained.

Measure and plan

Start here: get the area right before you buy anything.

Square footage calculator with an L-shaped room drawn to scale

Square footage calculator

Feet and inches as you measure them, L-shaped rooms, circles, subtractions, cubic yards, and a drawing of every area to scale.

CalculatorFeet & inchesCubic yards

Yard and garden

Beds, paths and driveways: sold by the bag, the cubic yard or the ton.

Coming
Mulch, gravel & topsoil
Bags vs. bulk, refresh mode for topping up, gravel in short tons. Coming before spring.

Heating and cooling

Sizing equipment, where bigger isn't better.

Coming
Window AC size (BTU)
ENERGY STAR sizing, and why an oversized unit feels cold and clammy. Coming before summer.

Walls and floors

Paint, flooring, tile and drywall, with the supplies that go with them.

Coming
Paint
Walls and ceiling on separate lines, primer on its own line, coverage by brand. Coming this spring.

Planned
Flooring
Boxes by material and pattern, with underlayment and trim.

Planned
Tile, grout & thinset
Waste by layout, grout by brand, thinset by trowel size.

Planned
Drywall
Sheets, mud, tape and screws on one list.

Concrete

Slabs, footings and posts.

Planned
Concrete
Bags by size or ready-mix, and where the line between them is.

How these calculators work

Three lines, every time. Exact amount → with waste → what to buy. Waste is for cuts and spills you'll use up; rounding to whole packages is listed separately and never sold to you as "leftovers".
Always rounded up. Rounding 47.2 bags down to 47 means a second trip to the store.
Real product numbers, with sources. Coverage and waste come from manufacturer data sheets. Numbers we couldn't verify aren't used for recommendations; you can type the one on your label instead.
Feet and inches as you measure them. 10' 6", 10 1/2 and 10-1/2 all work, and you can switch to metric at any time.
Print, share, offline. A one-page shopping list to take to the store, a link that holds your numbers (nothing stored on a server), and pages that keep working without a signal once you've opened them.

Which calculator do you need?

Tell me what you're trying to buy or build. The most-asked ones get built first.