BasCalc is a free online cement calculator built to make DIY concrete projects easier. Whether you're laying a shed base, pouring a garden path, or building a small foundation, working out exactly how much cement, sand and gravel you need can be confusing — especially when builders' merchants sell different bag sizes and recipe ratios vary.
This site exists to give a single, clear answer: enter your dimensions, get the exact materials list. No spreadsheets, no scribbled calculations on the back of an envelope.
BasCalc was built by a UK-based DIY enthusiast frustrated by the lack of clear, no-nonsense building calculators online. Most of the existing tools either bury the answer behind ads, don't account for waste, or only work in metric — which is a problem when half the recipe books and YouTube videos use imperial.
The site is intentionally simple. One calculator, the answer you came for, and supporting information if you want to dig deeper. No newsletters, no pop-ups, no sales pitches.
The calculator uses the standard 1:2:3 concrete mix ratio (1 part cement, 2 parts sharp sand, 3 parts gravel by volume), which produces roughly C20 grade concrete — strong enough for any standard domestic application including shed bases, paths and footings.
It automatically adds a 10% waste buffer to all material quantities, because in practice you always lose a bit to spillage, uneven ground, and mixing inefficiency. This means the figures you see are slightly higher than the mathematical minimum, but they reflect what you'll actually need to buy.
Cost estimates are based on average UK builders' merchant prices as of 2026 (around £7.50 per 25kg bag of cement, £55 per tonne of sharp sand, £50 per tonne of gravel). US prices use 80lb and 94lb bag conventions and average $5.50-6.50 per bag. Your local prices may vary — get a quote from your supplier for exact pricing.
The calculations are based on widely accepted construction industry standards and have been cross-checked against multiple authoritative sources (the UK's Department for Business and Trade, established builders' merchants, and concrete industry guidelines). However, every project is unique. Soil conditions, weather, mixing technique and material quality all affect the final result.
For structural work, load-bearing footings, or any project where failure could cause damage or injury, always consult a qualified builder or structural engineer. This site is intended as a planning aid for general domestic DIY work, not a replacement for professional advice.
Got a question, feedback, or spotted an error? Visit the contact page to get in touch.