Concrete Mix Ratio Calculator
A concrete mix ratio sets how much cement, sand and coarse aggregate go into a batch, written cement : sand : aggregate by volume — for example 1:2:4 or 1:1.5:3. This calculator turns a grade and a target volume into a full materials take-off: cement in kilograms and 50 kg bags, sand and coarse aggregate by weight or volume, and the mixing water.
It follows Indian nominal-mix practice (IS 456): the finished wet volume you want to pour is scaled up by a dry-volume factor, split by the mix ratio, and each part is converted to weight using its bulk density. Every constant — the dry factor, wastage, water/cement ratio and the three material densities — is shown and can be overridden, so nothing is a hidden number.
Crucially, the tool stays honest about strength grades. Fixed nominal ratios only exist up to M20; M25 is included as a widely-used convention with a caveat, and M30 and above are shown as design mixes with no invented ratio. Every calculation runs entirely in your browser.
How to use the concrete mix ratio calculator
Choose metric or imperial units at the top, pick a concrete grade, and enter the volume of finished, compacted concrete you need to pour. The results panel updates live with the cement, sand, coarse aggregate and water for that mix.
For a mix that is not on the list, choose Custom ratio and type your own cement : sand : aggregate parts by volume. Open the Assumptions & advanced card to change the dry-volume factor, wastage percentage, water/cement ratio, the three densities or the cement bag weight — the take-off recomputes as you edit.
How to work out a concrete mix in 5 steps
- Choose unitsSelect metric (m³, kg, litres) or imperial (yd³/ft³, lb, US gallons) at the top of the page.
- Pick a grade or a custom ratioChoose a grade from M5 to M25 for a nominal mix, or select Custom ratio and enter your own cement : sand : aggregate parts by volume.
- Enter the volumeType the volume of finished, compacted concrete you need to pour. Not sure of the volume? Use the linked concrete volume calculator first.
- Adjust the assumptionsOpen Assumptions & advanced to change the dry-volume factor, wastage, water/cement ratio, densities or bag weight if your materials differ from the defaults.
- Read the resultsRead the cement bags and weight, the sand and coarse aggregate (as weight or volume) and the mixing water — switch between total, per m³ and per bag, and print or export a CSV take-off.
Grade and mix ratio reference
The table below lists the standard nominal mix ratios by volume. Cement is always one part; the sand and aggregate parts grow as the grade gets leaner and weaker. A 1:2:4 mix (M15) means one part cement to two parts sand to four parts coarse aggregate, all measured with the same gauge box.
M5 to M20 are the IS 456 nominal mixes. M25 1:1:2 is listed because it is the single most-searched ratio, but it is an estimation convention only. M30 and above have no fixed ratio at all — see the next section for why.
| Grade | Ratio (c : s : a) | Status | Typical use |
|---|---|---|---|
| M5 | 1 : 5 : 10 | Nominal (IS 456) | Blinding, non-structural fill |
| M7.5 | 1 : 4 : 8 | Nominal (IS 456) | Blinding, levelling course |
| M10 | 1 : 3 : 6 | Nominal (IS 456) | Plain concrete, sub-base, PCC |
| M15 | 1 : 2 : 4 | Nominal (IS 456) | Plain concrete, flooring, light footings |
| M20 | 1 : 1.5 : 3 | Nominal (IS 456) | Reinforced slabs, beams, columns (housing) |
| M25 | 1 : 1 : 2 | Convention only — not IS 456 nominal | Reinforced concrete — estimate only; design mix required |
| M30 | — (no fixed ratio) | Design mix (IS 10262) | Reinforced concrete — lab-designed |
| M35 | — (no fixed ratio) | Design mix (IS 10262) | Structural / prestressed — lab-designed |
| M40 | — (no fixed ratio) | Design mix (IS 10262) | High-strength structural — lab-designed |
Nominal mix ratios at a glance
Each bar shows the cement, sand and coarse-aggregate proportions for a grade. Leaner grades such as M5 are mostly aggregate; richer grades such as M25 carry far more cement.
Nominal mix vs design mix
IS 456:2000 permits nominal mix concrete only up to M20. Nominal mixes use fixed, published proportions that are safe to batch by volume on site without a laboratory. Above M20, the code requires a design mix.
A design mix (IS 10262) is proportioned in the laboratory for your specific cement, aggregates and target strength, using trial batches. There is no single fixed ratio for M30, M35 or M40 — any ratio quoted for them is invented, so this calculator deliberately shows no quantities for design grades and points you to M20 or M25 nominal, or to a proper mix design, instead.
M25 1:1:2 sits in between. It is used almost universally for estimating, but it is not in the IS 456 nominal table, so the tool computes it while flagging it clearly as an estimation convention rather than a code-compliant nominal mix.
Why multiply by 1.54 (the dry-volume factor)
The volume you pour is compacted, wet concrete. The cement, sand and aggregate you buy are dry and loose, and they are full of air gaps. When you mix and compact them, those voids collapse and the total volume shrinks by roughly a third.
To go the other way — from the finished wet volume to the dry materials you must actually buy — you multiply by about 1.54. So 1 m³ of placed concrete needs roughly 1.54 m³ of dry, loose materials before mixing. This is a site estimation rule of thumb (commonly 1.54–1.57), not a code constant, and it is adjustable in the Assumptions card.
Materials per cubic metre by grade
The table below shows roughly how much of each material one cubic metre of each nominal grade needs, at the tool's default settings. It is a quick reference; the live calculator scales these to your volume, adds your wastage allowance and rounds cement up to whole bags for the pour.
| Grade | Cement (kg) | Sand (kg) | Aggregate (kg) | Water (L) |
|---|---|---|---|---|
| M5 (1:5:10) | 139 | 770 | 1444 | 69 |
| M7.5 (1:4:8) | 171 | 758 | 1422 | 85 |
| M10 (1:3:6) | 222 | 739 | 1386 | 111 |
| M15 (1:2:4) | 317 | 704 | 1320 | 158 |
| M20 (1:1.5:3) | 403 | 672 | 1260 | 202 |
| M25 (1:1:2) | 554 | 616 | 1155 | 277 |
Frequently asked questions
What is a concrete mix ratio?
A concrete mix ratio is the proportion of cement to sand to coarse aggregate, by volume, in a batch — written cement : sand : aggregate. For example, 1:2:4 (grade M15) is one part cement, two parts sand and four parts coarse aggregate. The parts are measured with the same gauge box or head-pan, and water is added separately according to the water/cement ratio.
How many bags of cement are needed per cubic metre?
It depends on the grade. For M20 (1:1.5:3) one cubic metre needs about 403 kg of cement, which is roughly 8 to 9 bags of 50 kg cement, plus about 672 kg of sand, 1260 kg of coarse aggregate and 200 litres of water at a 0.50 water/cement ratio. Leaner grades use fewer bags: M10 needs about 4 to 5 bags per m³. The calculator works this out for your exact volume.
Why is the dry-volume factor 1.54?
Placed concrete is compacted and wet, but the materials you buy are dry and loose with air voids between the grains. Mixing and compacting collapses those voids and the volume drops by about a third, so you need roughly 1.54 m³ of dry loose materials to make 1 m³ of finished concrete. It is a site estimation rule of thumb (commonly 1.54–1.57), not a fixed code value, and you can change it in the tool.
What is the mix ratio for M30, M35 or M40?
There isn't a fixed nominal ratio for M30 and above. IS 456 allows nominal mixes only up to M20; higher grades must be design mixes (IS 10262), proportioned in the lab for your specific materials and target strength using trial batches. Any single ratio quoted for M30–M40 is invented, so this calculator shows no quantities for design grades and recommends M20 or M25 nominal, or a proper mix design, instead.
Is M25 really 1:1:2?
1:1:2 is the ratio almost everyone uses to estimate M25, and the calculator computes it — but it is a convention, not a code-compliant nominal mix. M25 is not in the IS 456 nominal table, which stops at M20, so formally M25 requires a design mix. Treat the 1:1:2 figure as an estimate for ordering materials, not as a specification.
How much water do I add to concrete?
Water is set by the water/cement ratio: water (litres) ≈ w/c × cement weight (kg), since 1 litre of water weighs about 1 kg. A default of 0.50 is used here, so 400 kg of cement takes about 200 litres of water. Typical values run from 0.40 (strong but hard to place) to 0.60 (weaker, durability risk); the tool warns when you go outside that range.
What is the difference between a nominal mix and a design mix?
A nominal mix uses fixed, published proportions (like 1:2:4) that are safe to batch by volume on site without testing — IS 456 allows them up to M20. A design mix is proportioned in the laboratory for the actual cement, aggregates and target strength, with trial batches, and is required for M25 and above (M25 in practice, M30+ by code). Design mixes give better strength and economy but need lab input.
Does the calculator work in metric and imperial?
Both. Switch units at the top and every input and result converts: volume in m³ or cubic yards/feet, cement and aggregate in kg and tonnes or pounds and short tons, and water in litres or US gallons. The calculation runs in SI internally and is only converted for display, so switching units never changes the underlying answer.
Is the calculator private?
Yes. Every calculation runs entirely in your browser. Nothing you enter is sent to any server, and your settings are saved only in your own browser's local storage.