📖 How To Use
How to Use This Cylindrical Tank Volume Calculator
Getting your round tank's exact capacity takes under 30 seconds:
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Choose diameter or radius mode
Most tanks are measured across their widest point — that's the diameter. If you only have the radius (half the diameter), switch to Radius mode using the toggle at the top. Both give identical results.
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Enter the diameter (or radius)
Measure the internal diameter of your cylindrical tank — the distance across the inside, not the outside. Use whatever unit is on your tape measure: feet, inches, cm, m, or mm.
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Enter the height
Measure from the inside bottom to the maximum fill point. Height can use a different unit from diameter — this calculator converts everything automatically.
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Set the fill level (optional)
Drag the slider to calculate volume at a partial fill, e.g. 60% for a partially-filled tank. Leave it at 100% for full capacity.
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Hit Calculate
Results appear instantly — litres, US and UK gallons, cubic metres, weight in kg and lbs. Copy or print them with one click.
Tip: Cylindrical tanks often have a slight taper or domed base. For tapered tanks, use the average internal diameter. For tanks with a domed or cone-shaped bottom, subtract the dome volume using our Cone Bottom Tank Volume Calculator.
📐 The Formula
Cylindrical Tank Volume Formula
The volume of a cylinder is calculated using the radius (half the diameter) and the height. The key constant is π (pi ≈ 3.14159):
Volume = π × r² × h
Where: r = radius (half diameter), h = height
Litres (cm inputs): V (L) = π × r² × h ÷ 1,000
Cubic metres (m inputs): V (m³) = π × r² × h
Cubic feet (ft inputs): V (ft³) = π × r² × h
This calculator converts all dimensions to centimetres internally before calculating, so mixed-unit inputs (e.g., diameter in inches and height in metres) always produce correct results.
Worked Example
A cylindrical water tank with an internal diameter of 1.2 m and height of 1.5 m:
r = 1.2 ÷ 2 = 0.6 m
V = π × 0.6² × 1.5
V = 3.14159 × 0.36 × 1.5
V = 1.696 m³ = 1,696 litres
Unit Conversion Reference
| Unit | Equals Litres | From Litres |
|---|
| 1 Litre (L) | 1 L | × 1 |
| 1 Cubic Metre (m³) | 1,000 L | ÷ 1,000 |
| 1 US Gallon | 3.785 L | ÷ 3.785 |
| 1 UK Gallon | 4.546 L | ÷ 4.546 |
| 1 Cubic Foot (ft³) | 28.317 L | ÷ 28.317 |
| 1 Cubic Inch (in³) | 0.01639 L | × 61.024 |
Water Weight
1 litre of fresh water = 1 kg (or 2.2046 lbs). This is the standard used for structural load calculations worldwide.
Weight (kg) = Volume (litres) × 1
Weight (lbs) = Volume (litres) × 2.2046
📏 Reference Data
Standard Cylindrical Tank Sizes
Common manufactured cylindrical tank dimensions and their calculated volumes:
| Capacity | Diameter × Height (cm) | Diameter × Height (ft) | Litres | US Gal | Full Weight |
|---|
| 250 L | 60 × 90 | 2.0 × 3.0 | 254 | 67 | 254 kg |
| 500 L | 75 × 114 | 2.5 × 3.7 | 504 | 133 | 504 kg |
| 1,000 L | 100 × 128 | 3.3 × 4.2 | 1,005 | 265 | 1,005 kg |
| 1,500 L | 120 × 133 | 3.9 × 4.4 | 1,508 | 398 | 1,508 kg |
| 2,000 L | 130 × 151 | 4.3 × 5.0 | 2,007 | 530 | 2,007 kg |
| 5,000 L | 175 × 208 | 5.7 × 6.8 | 5,005 | 1,322 | 5,005 kg |
| 10,000 L | 230 × 241 | 7.5 × 7.9 | 10,035 | 2,650 | 10,035 kg |
Note: Actual manufacturer dimensions vary. Always verify against the supplier's data sheet. Dimensions shown are internal measurements.
❓ FAQ
Frequently Asked Questions
How do I calculate the volume of a cylindrical water tank?
Use the formula V = π × r² × h, where r is the radius (half the diameter) and h is the height. If your diameter is in centimetres, divide the result by 1,000 to get litres. This calculator handles all conversions automatically — just enter diameter (or radius) and height in any unit.
What is the difference between diameter and radius?
The diameter is the full width of the tank measured straight across the centre. The radius is exactly half the diameter — the distance from the centre to the edge. Use whichever you have; this calculator accepts both via the toggle button above the inputs.
Should I use internal or external diameter for the calculation?
Always use the internal diameter. The tank wall thickness (typically 5–15 mm for polyethylene, up to 50+ mm for concrete) reduces the usable internal space. Using the external diameter can overstate your tank capacity by 5–15% depending on wall thickness.
How heavy is a full cylindrical water tank?
Water weighs exactly 1 kg per litre. A 1,000-litre cylindrical tank carries 1,000 kg of water plus the tank shell (typically 20–50 kg for polyethylene, 100–200 kg for fibreglass). For rooftop installation, always confirm your structure can support the combined load. Use our Water Tank Weight Calculator for detailed load analysis.
How do I measure the diameter of an existing round tank?
For small tanks, place a straight rule or tape measure across the widest part. For larger tanks where measuring across is difficult, measure the circumference (all the way around the outside), then divide by π (3.14159) to get the external diameter, then subtract twice the wall thickness to get the internal diameter. Alternatively, most manufacturers stamp the nominal capacity on the tank — cross-check with this calculator.
Can I use this calculator for horizontal cylindrical tanks?
For a fully horizontal cylinder, this calculator gives the correct total capacity (the math is the same regardless of orientation). However, partial fill calculations are only accurate for vertical tanks — a horizontal tank's cross-section fills non-linearly. For partially-filled horizontal tanks, use our Horizontal Tank Volume Calculator.
How many litres per day does a household need?
WHO guidelines recommend at least 50 litres per person per day for basic needs. Most households in developed countries use 100–200 litres per person per day. A family of 4 typically consumes 400–800 litres per day. A 1,000-litre cylindrical tank provides 1–2 days of full-comfort supply for a family of 4.
What size cylindrical tank do I need for a home?
For residential use, a common rule is to store 3–5 days of household water. For a family of 4 using 150 L/person/day, that's 600–3,000 litres total. A 1,500 L cylindrical tank (approx. 1.2 m diameter × 1.33 m tall) covers 2–3 days at full comfort. Use our Tank Size for Home Calculator for a personalised recommendation.