🧱 Construction Calculators UK
Construction and home-improvement calculators for materials, mixes and build costs — concrete volumes, paint coverage, and more, worked out from your actual project dimensions rather than rough rules of thumb.
Building materials are expensive and mostly non-returnable, which makes over- or under-ordering a genuinely costly mistake. Concrete is sold by volume, so a slab, post hole and garage floor all need completely different quantities worked out from length, width and depth — not a generic per-square-metre guess. Paint coverage depends on wall area, number of coats and the specific product's stated yield, and getting it wrong means either a second trip to the merchant or litres of unused paint left over.
These calculators are built around the actual formulas tradespeople and DIYers use — converting your measurements into cement, sand, aggregate and bag counts, or into litres and tins of paint — so you can order close to what you'll actually need.
From the blog: How much concrete do I need? A homeowner's guide
All Construction calculators
Concrete Mix Calculator
Work out cement, sand, aggregate and bag quantities for a pour.
Paint Coverage Calculator
Estimate how many litres of paint and coats you need for a room.
Sand & Cement Render Mix
Calculate render mix ratios for wall rendering jobs.
House Extension Cost Calculator
Estimate a UK extension cost by type, size, region and spec.
Fencing Cost Calculator
Estimate panels, posts and cost for a garden fence.
Insulation U-Value Calculator
Estimate the U-value of a wall or roof build-up.
Roof Tile Quantity Calculator
Work out how many roof tiles you need by area.
Plasterboard Quantity Calculator
Calculate sheets of plasterboard needed for a room.
Skip Size Selector
Find the right skip size for your waste volume.
Frequently asked questions
How much extra material should I order over the calculated amount?
A buffer of around 5–10% is standard practice, since ground levels, formwork and wastage during mixing or application are rarely perfectly efficient. Running short mid-job is usually more costly and disruptive than having a small surplus.
Do these calculators account for different mix ratios?
Yes — mix ratio affects how much cement versus sand and aggregate you need for a given volume, and stronger, load-bearing mixes use proportionally more cement. Always check manufacturer guidance for structural work.