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Home › Water Tank Cleaning › Capacity Calculator
Find out how many litres your water tank holds. Enter the tank’s dimensions below, pick the shape, and get the capacity instantly. Works for rectangular tanks, round Sintex tanks and horizontal cylindrical tanks, in feet, metres, centimetres or inches.
Enter internal dimensions for the most accurate result. Capacity is shown in litres, with cubic metres and gallons too.
Capacity is simply the internal volume of the tank converted to litres. Measure the inside of the tank, not the outside, because the walls take up space. Once you have the volume in cubic metres, multiply by 1,000, since one cubic metre of water is exactly 1,000 litres. The calculator above does the unit conversion and the arithmetic for you, but the formulas are below if you want to check by hand.
| Tank shape | Formula (dimensions in metres) |
|---|---|
| Rectangular / square | Length × Width × Height × 1000 = litres |
| Round vertical (Sintex) | π × (Diameter ÷ 2)² × Height × 1000 = litres |
| Horizontal cylinder (full) | π × (Diameter ÷ 2)² × Length × 1000 = litres |
| Horizontal cylinder (part full) | Circular-segment area at the fill depth × Length × 1000 |
A quick worked example: a rectangular sump 2m long, 1.5m wide and 1.5m deep holds 2 × 1.5 × 1.5 = 4.5 cubic metres, which is 4,500 litres. A round Sintex tank 1.1m across and 1.2m tall holds 3.1416 × 0.55 × 0.55 × 1.2 × 1000, or about 1,140 litres.
Typical overhead and Sintex tanks in Delhi NCR homes, as a rough reference. Your exact figure depends on the internal dimensions, so measure and use the calculator for accuracy.
| Tank | Approx. dimensions | Capacity |
|---|---|---|
| Small overhead (1 BHK) | ≈ 0.9m round × 0.8m tall | 500 L |
| Medium Sintex (2 BHK) | ≈ 1.1m round × 1.2m tall | 1,000 L |
| Large Sintex (kothi) | ≈ 1.5m round × 1.4m tall | 2,000 L |
| Underground sump | ≈ 2m × 1.5m × 1.5m | 4,500 L |
| Society master tank | ≈ 3m × 2.5m × 2m | 15,000 L |
How do I calculate the capacity of a water tank in litres?
Multiply the internal length × width × height in metres to get cubic metres, then multiply by 1,000 for litres. For a round tank use π × radius² × height × 1,000. A 1m × 1m × 1m tank holds 1,000 litres.
What is the formula for a Sintex or round tank?
A round vertical tank is a cylinder: litres = 3.1416 × (diameter ÷ 2)² × height, all in metres, × 1,000. So a 1m-wide, 1.4m-tall Sintex tank holds roughly 1,100 litres.
Does capacity mean the water it actually holds?
Capacity is the full internal volume. Usable water is a little less because tanks are never filled to the brim and the outlet sits above the base, so plan for about 90–95% of the calculated figure. The calculator shows a usable estimate at ~92%.
How often should a tank this size be cleaned?
Every 3–6 months regardless of size, since sediment and biofilm build up at the bottom where you cannot see it. Knowing the litres also helps you price a cleaning: see the cost calculator.
Now you know the size, estimate the cleaning price with our water tank cleaning cost calculator, see full service details on the Water Tank Cleaning page, or book underground sump cleaning and society / RWA contracts directly. Read our guide to water tank cleaning costs in Delhi for more.