Work out how much to buy before you get to the checkout
Ten calculators for concrete, paint, tile, flooring, mulch, gravel, fencing and running costs. Enter the room or the area, get the quantity, add the waste allowance the trade actually uses.
The expensive mistakes in a home project are almost never the skill. They are the second trip to the merchant because a bag of mortar ran short, or the four unopened boxes of tile that cannot go back. Both come from guessing a quantity that a minute of arithmetic would have settled.
Each calculator here asks for the measurements you already have, applies the standard coverage rate for the material, and adds a waste allowance you can see and adjust. The result is a shopping quantity, not an abstract area figure you still have to convert.
No tool matches that.
Building
- Concrete Calculator
Work out how many cubic yards or bags of concrete you need for a slab, footing, or post hole.
- Drywall Calculator
Work out how many drywall sheets, screws, and joint compound a room needs.
Finishing
- Paint Calculator
Find out how many gallons of paint you need for a room, including coats and trim.
- Flooring Calculator
Calculate the square footage and boxes of flooring you need, with a waste-factor buffer.
- Tile Calculator
Find how many tiles, how much grout, and how much adhesive a floor or wall needs.
Outdoor
- Mulch Calculator
Find the cubic yards or bags of mulch you need for your garden beds.
- Gravel Calculator
Calculate the tons or cubic yards of gravel needed for a driveway, path, or base layer.
- Fence Calculator
Find the posts, rails, and panels you need for a fence of any length.
Systems
- BTU Calculator
Estimate the heating or cooling BTU capacity a room needs based on its size.
- Electricity Cost Calculator
Find out what it really costs to run an appliance, from its wattage and your electricity rate.
From the blog
Pick the calculator for the job
Working on surfaces? Paint, tile and flooring all start from the same room measurements, then diverge: paint accounts for coats and coverage per litre, tile for grout lines and the cuts around edges, flooring for pack sizes and the offcut you lose to the pattern.
Pouring or filling? Concrete, mulch and gravel are volume problems, so depth is the input people get wrong most often. Each of these asks for it explicitly and shows how sensitive the total is to a few extra centimetres.
Running costs rather than materials? The electricity cost calculator turns a device's wattage and hours of use into a monthly figure, and the BTU calculator sizes heating or cooling to a room rather than to a salesperson's guess.
About the waste allowance
Every quantity here includes an adjustable overage, defaulted to the range trades normally allow: around ten per cent for paint and flooring, more for tile once you have diagonal cuts or a patterned layout. Ordering the exact calculated amount is how a project stalls.
The figures assume standard materials and a reasonably regular space. Awkward rooms, unusual substrates and anything structural deserve a second opinion from whoever is doing the work.
Common questions
Do these work in metric and imperial?
Yes. Enter feet or metres, litres or gallons, and the result comes back in units that match what you typed. Nothing here assumes one measurement system.
How much extra should I order?
Ten per cent covers most straightforward jobs. Go to fifteen for tile with diagonal cuts or a repeating pattern, and higher again for flooring with a long pattern repeat. Each calculator lets you change the allowance and shows the effect immediately.
Are the coverage rates reliable?
They are the standard published rates for common materials, which is what a merchant's own estimator uses. Your actual product may differ, so check the tin or the pack, especially for paint on porous or previously unpainted surfaces, which drinks far more than the label suggests.
Can I use these for a quote?
They are good enough to sanity-check a quote and to plan a shop, which is what most people need. For anything structural, or where being wrong is expensive, treat the number as a cross-check on a professional's figure rather than a replacement for it.
Is there a signup?
No. Every calculator runs in your browser, nothing is stored, and the site is paid for by clearly labelled ads.