How to use the Concrete Mix Design Calculator (IS 10262)
- 1. Set the grade and exposureChoose the grade, RCC or PCC, exposure and site control.
- 2. Enter materialsw/c from Fig. 1, aggregate size, shape, slump, zone, admixture and specific gravities.
- 3. Get the trial mixCement, water, sand and coarse aggregate per m³ and per bag, with the working.
IS 10262:2019 steps
- Target strength: f'ck = the higher of fck + 1.65S and fck + X. Assumed S is 3.5, 4, 5 or 6 N/mm² and X is 5, 5.5, 6.5 or 8 for M10-15, M20-25, M30-60 and M65 and above.
- w/c ratio: from Fig. 1 for your cement, then limited to the IS 456 Table 5 maximum for the exposure.
- Water: 208, 186 or 165 kg/m³ for 10, 20 or 40 mm angular aggregate at 25-50 mm slump, about +3% per extra 25 mm slump, less for rounded aggregate and water-reducing admixtures.
- Cement = water / (w/c), at least the Table 5 minimum.
- Coarse aggregate volume from Table 5 by size and sand zone at w/c 0.5, ±0.01 for every ∓0.05 change in w/c.
- Absolute volume: aggregate volume = 1 − air − cement − water − admixture volumes, split into coarse and fine and multiplied by specific gravity.
Worked example: M25, 20 mm, moderate exposure
Target = 25 + 1.65 × 4 = 31.6 N/mm² (higher than 25 + 5.5). Take w/c 0.45 (below the 0.50 maximum). Water = 186 × 1.06 = 197.2 kg for 100 mm slump. Cement = 197.2 / 0.45 = 438 kg. Coarse aggregate fraction for zone II = 0.62 + 0.01 = 0.63. Aggregate volume = 1 − 0.01 − 0.139 − 0.197 = 0.654 m³, giving about 1129 kg coarse and 641 kg fine aggregate.
This is a trial mix. Make trial batches, check slump and cube strength, and adjust. The table values used here are the commonly cited code values; check them against your copy of IS 10262 and IS 456.
Exam and lab tips
- Write the durability check (max w/c, min cement, min grade) as a separate step; examiners look for it.
- Cement above 450 kg/m³ needs attention: use an admixture or a mineral admixture.
- Quantities are for saturated surface-dry aggregate. Correct the water for free moisture or absorption on site.
For a quick nominal-mix estimate use the cement, sand and aggregate calculator.
Frequently asked questions
Is this mix ready to use on site?
No. IS 10262 gives a starting proportion. It must be confirmed by laboratory trial mixes for workability and strength before use.
Why do I have to enter the w/c ratio?
IS 10262:2019 reads it from curves in Fig. 1 that depend on your cement's 28-day strength. Read the value there and enter it. The tool then applies the IS 456 maximum.
Does it handle fly ash or slag?
Not yet. This version covers OPC-type mixes with a chemical admixture. Fly ash and slag mixes need the extra steps in the code.
Can I change the code table values?
Yes. Standard deviation, X, max w/c, base water, coarse aggregate fraction, air and minimum cement all have blank boxes that override the table value.
Is this calculator free?
Yes. You enter your name and WhatsApp number once to see your result, and all other Uncodemy tools then open without the form. Everything is calculated in your browser.