Water Tank Calculator
Calculate tank volume in Liters and estimate how long water will last for your household.
All dimensions in feet
Standard urban usage: 135 L/person/day
Tank Capacity
1,795 Gallons | 240.0 ft³
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What is a Water Tank Calculator?
A Water Tank Calculator helps you determine the capacity of your water storage tank and estimate how long the stored water will last for your household. Whether you're building a new underground sump or buying an overhead plastic tank, knowing the exact capacity in Liters is essential for planning.
Contractors often quote tank sizes in "cubic feet" but water consumption is measured in Liters. Our calculator instantly converts dimensions to Liters, Gallons, and also shows the structural weight when full - critical for overhead tank installations.
The calculator also estimates how many days your tank will last based on household size and daily water consumption, helping you plan for water shortages.
Tank Presets
Quick-select common sizes: Small/Medium/Large Sump and 500L/1000L/2000L Overhead tanks.
Two Shapes
Support for Rectangular (sump) and Cylindrical (overhead) tanks with appropriate formulas.
Usage Estimation
Calculate how many days water will last based on household size and customizable daily usage.
Multiple Units
Results in Liters, Gallons, and Cubic Feet. Input dimensions in Feet, Meters, or Inches.
How to Use the Water Tank Calculator
Select Preset or Custom
Choose from 7 common tank sizes or select Custom to enter your own dimensions.
Choose Tank Shape
Select Rectangular for underground sumps or Cylindrical for overhead tanks.
Enter Dimensions
Input L × W × D for rectangular or Diameter × Height for cylindrical.
Get Results
View capacity in Liters/Gallons, days water lasts, and structural weight.
Rectangular Tank (Sump)
Common for underground water storage. Made from RCC (cement concrete) or brick masonry with waterproof plaster.
Example: 8ft × 6ft × 5ft = 240 ft³ = 6,800 Liters
Standard depths: 4-6 feet for residential. Keep L:W ratio between 1:1 to 2:1 for structural stability.
Cylindrical Tank (Overhead)
Common for overhead storage. Usually made from HDPE plastic (Sintex, Ganga, etc.) or stainless steel.
Example: Dia 4ft × H 3ft = 37.7 ft³ = 1,068 Liters
Standard sizes: 500L, 750L, 1000L, 2000L. Check roof load capacity before installation.
Daily Water Consumption Guide
| Activity | Usage/Person | Notes |
|---|---|---|
| Bathing | 50-60 L | Bucket bath ~40L, Shower ~80L |
| Toilet Flushing | 25-35 L | 6-10L per flush, ~5 times/day |
| Laundry | 15-25 L | Machine ~60L per load |
| Cooking/Drinking | 10-15 L | Includes utensil washing |
| Total | ~135 L/day | Standard urban estimate |
Pro Tips for Water Tank Planning
Plan for 3-day backup - Size your sump for at least 3 days of water needs.
Check roof load - 1000L tank = 1 Tonne. Verify structural capacity.
Use ISI marked tanks - Look for IS:12701 certification for plastic tanks.
Install overflow pipe - Prevent tank overflow and water wastage.
Cover tanks properly - Prevent mosquito breeding and contamination.
Clean annually - Drain and clean tanks at least once a year.
Common Use Cases
New Home Construction
Size underground sump and overhead tank before construction. Plan pump capacity based on height.
Apartment Buildings
Calculate total storage needed for all residents. Plan for common sump with multiple overhead tanks.
Water Shortage Planning
Calculate how long current storage lasts during water cuts. Plan tanker water quantity needed.
Frequently Asked Questions
How do I calculate water tank capacity in Liters?
For rectangular tanks: Volume (L) = Length × Width × Height in meters × 1000. For cylindrical tanks: Volume (L) = π × (Diameter/2)² × Height in meters × 1000. Our calculator handles unit conversion automatically - just enter dimensions in your preferred unit.
How much water does a person use per day?
Average urban water consumption is 135 Liters per person per day. This includes bathing (55L), toilet flushing (30L), laundry (20L), cooking (15L), and drinking/cleaning (15L). Rural areas may use less (100L), while luxury homes may exceed 200L per person.
What size water tank do I need for a family of 4?
A family of 4 using 135L/person/day needs 540 Liters daily. For 3-day backup, you need 1,620L minimum. We recommend 2,000-3,000L (2-3 cubic meters) underground sump for residential use. This provides adequate buffer for irregular water supply.
How heavy is a full water tank?
Water weighs 1 kg per Liter. A 1,000L tank weighs 1 Tonne (1,000 kg) when full - plus tank weight. A 5,000L sump weighs over 5 Tonnes. This is critical for overhead tanks - ensure your roof structure can support the full weight, not just the empty tank.
What is the difference between sump and overhead tank?
Sump (underground tank) stores water at ground level, typically rectangular RCC construction. Overhead tank is elevated on roof/stand, usually cylindrical plastic (Sintex type). Water flows from sump to overhead via pump, then gravity-feeds to taps. Most homes have both.
How do I convert cubic feet to Liters?
1 Cubic Foot = 28.3168 Liters. Contractors often quote tank size in cubic feet, but water billing is in Liters. Our calculator shows both units. Example: A 100 cubic feet tank holds 2,832 Liters (about 750 Gallons).
What is the standard overhead tank size for homes?
Common overhead tank sizes: 500L for 1-2 people, 1000L for 3-4 people, 2000L for 5-6 people. These provide 1-2 days backup. For areas with unreliable water supply, consider larger sizes or multiple tanks. Always check roof load capacity.
How do I calculate underground sump dimensions?
For a given volume: Choose practical depth (4-6 feet for residential). Calculate area needed = Volume ÷ Depth. Choose L:W ratio of 1.5:1 to 2:1. Example: For 5000L (177 cubic feet) at 5ft depth, you need 35 sq ft area, approximately 7ft × 5ft.
Can I use this calculator for swimming pools?
Yes, the rectangular tank calculation works for pools. Enter pool length, width, and average depth. For pools with varying depth (shallow to deep end), use average depth. Our calculator shows volume in Liters and Gallons - useful for chemical dosing calculations.
What material is best for water tanks?
Underground sumps: RCC (concrete) is most durable and economical. Overhead tanks: HDPE plastic (Sintex type) is lightweight, food-safe, and UV resistant. Stainless steel is premium but expensive. Never use galvanized iron for drinking water - zinc leaches over time.