Cement/Sand/Stone Mix Ratio Calculator

Cement, sand, and stone quantities from a mix ratio

This cement, sand, and stone mix ratio calculator helps you split a target mix volume into its component parts. If you are working from a ratio like 1:2:3, you already know the proportions, but you still need real quantities to order materials, plan deliveries, and avoid running short mid job. This tool converts the ratio into volumes for cement, sand, and stone based on the total volume you want to make.

You start by entering your total mix volume in either cubic meters (m³) or liters (L). Then enter the ratio as “parts” for cement, sand, and stone. The calculator adds the parts together and allocates the total volume in the same proportions. For example, a 1:2:3 mix has 6 total parts, so cement is 1/6 of the volume, sand is 2/6, and stone is 3/6. The result is the simplest way to estimate quantities when you are measuring by volume on site.

The calculator also includes an optional waste or spillage allowance. On real jobs, you rarely place exactly what you planned. You lose a bit to handling, cleanup, uneven formwork, or over ordering to stay safe. Adding a small percentage can prevent the common situation where you are a wheelbarrow short at the end, which usually costs more time and money than the extra material would have.

Finally, you can choose a cement bag size to get an estimated number of bags. This estimate is there to help you plan purchasing and transport, not to replace supplier guidance. Cement is sold by mass (kg), while this calculator is allocating by volume. To bridge that gap, the bag estimate uses a typical bulk density assumption for bagged cement to approximate a bag’s volume. It is useful for rough planning, especially for smaller pours and repairs where you are buying bagged cement rather than ordering ready mix.

What you get back is a clear split of cement, sand, and stone volumes in both liters and cubic meters. That makes it easy to cross check against the units you actually buy in. Many suppliers quote sand and stone by cubic meters, while site mixing is often measured in buckets or wheelbarrows. Seeing both units reduces mistakes and makes your plan easier to communicate.

Assumptions and how to use this calculator

• The ratio is treated as a volume ratio (parts by volume), which is the most common approach for quick site batching.
• The total mix volume is assumed to be the combined wet mix volume you want to produce. Real yields can vary because aggregate grading and moisture affect packing.
• The cement bag estimate uses a rough conversion based on a typical cement bulk density (about 1,440 kg/m³). This implies about 34.7 L per 50 kg bag and about 17.4 L per 25 kg bag.
• Moisture in sand and aggregate can change the effective volume and water demand. This calculator does not adjust for moisture content.
• If you need high accuracy (structural concrete, engineered mixes, or compliance work), follow the mix design or supplier specification and use measured batching and testing.

Common questions

Is a 1:2:3 mix always correct for concrete?

No. 1:2:3 is a common general purpose site mix, but the “right” mix depends on strength requirements, aggregate size, workability, exposure conditions, and the cement type. Use this calculator to split a ratio you have already chosen, then confirm the ratio is appropriate for the job and local standards.

Why does the calculator use parts instead of kilograms?

Most ratio based mixes on site are measured as parts by volume because it is faster and does not require scales. Cement is usually bought by mass, so the calculator provides a bag estimate as a convenience. For engineered work, mass batching and proper mix design are more reliable.

Should I include water in the ratio?

This calculator focuses on cement, sand, and stone. Water is usually controlled separately because it depends on moisture in aggregates, desired slump, and the water to cement ratio needed for strength and durability. Adding too much water is one of the fastest ways to weaken concrete, so treat water as a controlled variable.

What waste percentage should I use?

For small mixes and careful work, 2% to 5% is often enough. For messy handling, uneven formwork, or when you are not sure about volume measurements, 5% to 10% can be more realistic. If you are budgeting tightly, start lower and increase only when your job conditions justify it.

Why might my actual yield be different from the calculated volumes?

Aggregates pack together in ways that change void space, and moisture can change effective volume and workability. Mixing method, vibration, and compaction also affect final placed volume. Treat these results as a planning estimate and adjust based on your material behavior and past experience.