What is the Concrete Mix Calculator?
Calculate cement, sand, aggregate, and water for concrete with this free concrete mix calculator. Design by volume (m³ or yd³), number of cement bags, or grade presets M10–M25 (1:3:6 through 1:1:2). Enter water–cement ratio and custom C:S:A proportions. Get material weights, bag count, and water in liters or gallons. Metric and imperial units. Runs instantly in your browser.
How to use the Concrete Mix Calculator
- Choose By Volume, By Cement Bags, or By Grade (M10–M25).
- Select metric or imperial units.
- Enter concrete volume or bag count, mix ratio, and w/c ratio.
- Adjust bag weight if not using 50 kg or 94 lb bags.
- Review cement, sand, aggregate, water quantities and copy results.
Common use cases
- Estimating materials for a house slab or driveway pour
- Planning cement bags to buy for a footing volume
- Comparing M15 vs M20 material requirements
- Site crew batching from bag count and ratio
- Construction coursework on mix design basics
Frequently asked questions
- What is a concrete mix ratio?
- Mix ratio 1:S:A means 1 part cement to S parts sand (fine aggregate) to A parts coarse aggregate by weight. M15 is commonly 1:2:4; M20 is 1:1.5:3.
- What water–cement ratio should I use?
- Lower w/c gives stronger, less workable concrete. Typical ranges: M25 ~0.40, M20 ~0.45, M15 ~0.50. Hot weather may need careful water control; this tool uses your entered w/c directly.
- How many bags of cement per m³?
- It depends on grade and w/c. M20 at ~5 m³ might need roughly 30–40 bags of 50 kg cement — use this calculator with your volume and grade for a specific estimate.
- Is this nominal or design mix?
- These are nominal mix proportions for estimation and site planning. Structural concrete should follow code-approved design mixes and lab trials.
- What bag sizes are supported?
- Default is 50 kg (metric) or 94 lb (US). You can change bag weight for 40 kg, 80 lb, or other regional sizes.
