Home project calculators

Ten calculators tell you how much to buy for a home project: bags of concrete for a slab, mulch for a bed, boxes of flooring, tiles and their cuts, paint, wallpaper rolls, deck boards, drywall sheets, fence posts and pickets, and the BTU rating for a room air conditioner or heater. Purchase counts always round up, and each page says where its numbers come from, or says plainly when a default has no published source. Three short guides cover waste factors, slab thickness and coats of paint.

Which calculator do you need?

All ten answer the same question, which is how much to buy. What changes is the unit the store sells it in.

Project	What you buy	Tool
Pouring a slab	Bags of mix, by weight	Concrete calculator
Topping up beds	Bags by cubic foot, or bulk yards	Mulch calculator
Laying a floor	Whole boxes, by square foot	Flooring calculator
Painting walls, or walls and a ceiling	Gallons and quarts of paint	Paint calculator
Papering walls	Rolls, packed as drops	Wallpaper calculator
Tiling a room or a backsplash run	Tiles, by count and cut size	Tile calculator
Decking a rectangle or an L	Boards by length, with a cut plan	Deck board calculator
Hanging drywall	Sheets, screws, compound and tape	Drywall calculator
Building a board fence	Posts, rails, pickets and concrete	Fence calculator
Sizing a room air conditioner or heater	BTU per hour, with each factor shown	BTU calculator

Why does every count here round up?

Because the cost of the two mistakes isn't symmetrical, and it isn't close.

Order one box of flooring too many and you've spent one box. Order one too few and you're back at the store hoping the next box is the same dye lot, which it often isn't. Run short on concrete mid-pour and you get a cold joint, a permanent weak seam in the slab you just paid to place.

So purchase counts round up, never down. What we don't do is hide the rounding. Each tool prints the leftover next to the count. Flooring leftover is ordered material minus the area after waste; other tools use the area or volume you entered. You can see what the rounding cost you, and you can see what a layout choice cost you on top of that.

Where do the numbers come from?

Every constant on these pages is attributed on the page that uses it. That's the habit these pages are built on, because a material calculator is only as good as the figure buried inside it.

• Concrete bag yields come from QUIKRETE, which publishes that all yields are approximate. We repeat that on the page rather than presenting a bag count as exact.
• Mulch bag conversion starts from the definition of a cubic yard: 27 cubic feet, which is thirteen and a half two-cubic-foot bags.
• Flooring waste ranges follow the Cavalieri Flooring layout taxonomy, from five percent for a plain rectangle up to twenty-five percent for chevron.
• Mulch depth follows University of Illinois Extension guidance, which separates composted from coarse mulch.

Is ten percent waste really an industry standard?

Not in the way the phrase suggests, and this is the most useful thing on this page.

We read the 2025 NWFA Wood Flooring Installation Guidelines cover to cover. Part IV covers conversions. The guidelines contain no waste or overage percentage at all. Ten percent is trade consensus, repeated by suppliers and installers, and that's a different kind of number from a published standard.

It's still a reasonable default for most residential jobs. It just isn't a rule you can cite, and the layout you're actually installing moves it more than any rule of thumb does. The full taxonomy is in how much waste to add, with the ranges laid out by layout type. When a preset is a range, the flooring calculator uses the top of it: ordering long costs one box, ordering short risks a second dye lot. Tile is counted by piece, not by box area. The tile calculator lays a rectangle at your tile size and grout gap, then prints every edge cut. Straight grid and brick offset are simulated. Diagonal, herringbone, and chevron stay sourced estimates and say so: the tile calculator takes the low end of each range, then adds its breakage allowance. Paint volume is a required scope choice first: the paint calculator will not guess whether you are covering the ceiling. Wallpaper is counted as drops, not square feet: the wallpaper calculator packs every wall onto the same rolls and names what is left on the last one.

Concrete overage works the same way. It's trade convention rather than a standard, it's optional on the page, and it carries a visible footnote saying so.

Why doesn't the mulch calculator have a waste factor?

Mulch settles. Adding a percentage on top of a settled-depth estimate is guessing twice.

The mulch calculator treats depth as the variable instead. You pick two, three, or four inches and see the purchase count for each, which is the decision you're actually making in the garden center aisle. The depth series table puts all three side by side.

One quirk worth knowing: the sourced conversion and the purchasable count are different numbers. A cubic yard is thirteen and a half two-cubic-foot bags in the arithmetic and fourteen bags at the store. Both are shown, because rounding one into the other silently is how a sourced figure stops being sourced.

Why a thickness series instead of one answer?

On a slab, thickness is usually the thing you're still deciding. Four inches for a patio, six if a vehicle will sit on it, and the difference in bags is not small.

So the concrete calculator prints the same footprint at three, four, five, and six inches, against forty, sixty, and eighty pound bags. One table, twelve answers, no re-entering your dimensions to compare.

Where do your measurements go?

Nowhere. Slab dimensions, bed areas, and room sizes stay in the tab. Share links carry state after the hash mark, which browsers don't transmit to a server, so sending a link to a contractor rebuilds the inputs on their machine without routing them through ours.

Each page shows its own measured request count and script weight while you use it, so the claim is checkable on the page making it. Once a tool has loaded, you can turn your wifi off and keep working. The method is written up in how we build tools.

Questions

Can I add up several rooms at once?

Yes. In the flooring calculator, enter the first room, then click Add area for each other room, up to ten in all, and split an L shaped room into two rectangles. It totals the areas first and then adds your layout waste, so the waste is figured on the whole job, not room by room.

Which bag weight should I pick for concrete?

Whichever you can lift and your store stocks. A cubic yard takes 45 bags of 80 lb or 90 bags of 40 lb, so 40 lb bags mean twice as many bags to carry, at half the weight each. The concrete calculator lists 40, 60 and 80 lb counts side by side at each thickness. Pick 90 lb and that column joins the table.

How carefully do I need to measure?

To the inch. A calculator can't see your tape measure. Write down a room as 12 feet when it's really 12 feet 4 inches, and a 12 foot wide floor comes up 4 sq ft short. The concrete and flooring calculators take feet and inches, like 12 ft 4 in, so enter the odd inches instead of rounding them off.

Should I buy the cheapest bag?

Compare the price per cubic foot, not the price per bag. An 80 lb bag of QUIKRETE 1101 yields about 0.60 cubic feet and a 40 lb bag about 0.30, per its data sheet, so divide each price by its yield. The concrete calculator takes an optional cost per bag and shows an estimated total for the weight you picked. The tile calculator takes a price per box.

Flooring works differently. Each product sets its own coverage per box, so once you pick the floor, the box count follows from your area and layout waste.

Do these handle circles, curves, or stairs?

Not directly. The concrete calculator handles rectangular slabs only, so round slabs, footings, columns and stairs are out. For a curved bed, work out the area first. The mulch calculator takes square feet, and a round bed 10 feet across is about 78.5 sq ft. The tile calculator has a Total area mode for the same trick. For flooring, split an odd room into rectangles.

Related tools

For date and time planning rather than materials, use the date and time tools. Material changes land in the changelog.