Concrete Ratio Calculator
Calculate cement, sand, and gravel proportions for any concrete grade. Select a mix design (M10 to M25), enter the volume you need, and get exact material quantities in kilograms — with a live stacked bar chart showing mix proportions.
What Are Concrete Mix Ratios?
A concrete mix ratio defines the proportion of cement, sand (fine aggregate), and gravel (coarse aggregate) used to create concrete. Written as C:S:G, a ratio of 1:2:3 means one part cement to two parts sand to three parts gravel by volume or weight. The ratio directly determines the concrete's compressive strength, workability, and durability.
Different construction applications demand different mix ratios. A lean mix like 1:3:6 (M10) works for non-structural leveling courses, while a rich mix like 1:1:2 (M25) provides the strength needed for load-bearing beams and columns. The Concrete Ratio Calculator helps you choose the right mix and calculate exact material quantities for any project volume.
Formulas & Equations Used
This Concrete Ratio Calculator uses the following core equations:
1 Material Quantity per Cubic Meter ▼
For a 1:2:3 mix in 1 m³ (~2,400 kg total): Cement = 2400 × 1/6 = 400 kg. Sand = 2400 × 2/6 = 800 kg. Gravel = 2400 × 3/6 = 1,200 kg.
2 Water-Cement Ratio ▼
A W/C of 0.45 with 350 kg cement means 350 × 0.45 = 157.5 liters of water. Lower W/C = stronger concrete but harder to pour.
3 Number of Cement Bags ▼
If you need 350 kg of cement: 350 ÷ 50 = 7 bags. Always round up to the nearest whole bag.
4 Volume to Weight Conversion ▼
Material densities vary. Cement bags are approximately 1,440 kg/m³. Dry sand is roughly 1,600 kg/m³. Crushed gravel averages 1,500 kg/m³.
How to Use This Concrete Ratio Calculator
Follow these 3 simple steps:
Select Your Grade
Choose a concrete grade (M10 to M25) or enter a custom cement:sand:gravel ratio for your specific project requirements.
Enter Volume Needed
Specify how many cubic meters of concrete you need. The calculator computes exact quantities of cement, sand, and gravel.
Get Material List
View the exact weight in kilograms for each material, number of cement bags, water volume, and a visual proportion breakdown.
Example Problems & Step-by-Step Solutions
Here are 3 worked examples using this Concrete Ratio Calculator:
Example 1 Calculate materials for 2 m³ of M15 concrete (1:2:4)
Example 2 Find water needed for M20 concrete with W/C = 0.45
Example 3 Compare M10 vs M25 material costs for a 5 m³ slab
Interactive Concrete Mix Adjuster
Select a concrete grade to see the standard mix ratio, then adjust sliders to customize the proportions. The stacked bar chart updates in real time to show each material's percentage of the total mix.
Concrete Grade Comparison Chart
Each concrete grade specifies a minimum compressive strength at 28 days. Higher grades use more cement relative to aggregates, producing stronger but more expensive concrete. Choose the grade that matches your project's structural requirements — over-specifying wastes money, under-specifying risks failure.
| Grade | Mix Ratio | Strength | Typical Use |
|---|---|---|---|
| M10 | 1:3:6 | 10 MPa | Lean concrete, leveling |
| M15 | 1:2:4 | 15 MPa | Floors, foundations |
| M20 | 1:1.5:3 | 20 MPa | Slabs, beams, columns |
| M25 | 1:1:2 | 25 MPa | Heavy structural work |
Frequently Asked Questions
What is the standard concrete mix ratio?▼
The standard concrete mix is 1:2:3 (cement:sand:gravel by volume). This M15 grade mix produces concrete with approximately 15 MPa compressive strength after 28 days, suitable for most residential foundations, footings, and sidewalks.
How much cement do I need for 1 cubic meter of concrete?▼
For a 1:2:3 mix, you need approximately 320-350 kg of cement per cubic meter. The exact amount depends on cement density, aggregate size, and the water-cement ratio. For a 1:2:4 mix, it drops to about 280-300 kg.
What is the water-cement ratio and why does it matter?▼
The water-cement ratio (W/C) is the weight of water divided by the weight of cement. A W/C of 0.45-0.50 is common for structural concrete. Lower ratios produce stronger, less permeable concrete but are harder to work with. Every 0.05 increase in W/C drops compressive strength by roughly 10%.
What is the difference between M15 and M25 concrete?▼
The "M" stands for mix and the number is the compressive strength in MPa at 28 days. M15 (1:2:4) is for general construction like floors and footpaths. M25 (1:1:2) is for structural elements like beams, columns, and retaining walls that carry heavy loads. M25 uses roughly 2.5× more cement per cubic meter.
Can I mix concrete by volume instead of weight?▼
Volume mixing is acceptable for small DIY projects. Professional work uses weight (batching by mass) for accuracy. Volume ratios are less precise because sand moisture content changes its volume — wet sand can have 20-30% more bulk volume than dry sand due to a phenomenon called "bulking."
How long does concrete take to cure?▼
Concrete reaches about 50% of its design strength in 3 days, 75% in 7 days, and 99% in 28 days. Full curing continues for months. Keep concrete moist for at least 7 days after pouring for optimal strength development. The mix ratio doesn't change curing time, but it determines the final strength achieved.