RC Reminder Calculator

Cylinder Volume Tank Calculator

Calculate the total capacity and current fill level of cylindrical tanks. Enter the tank dimensions to get volume in litres, gallons, or cubic meters. Works for vertical standing tanks and horizontal lying tanks.

Tank Volume Calculator

V = πr²h
75% 50% 25% Tank Capacity

Vertical Cylindrical Tanks

V = πr²h (vertical tank)

Vertical tanks stand upright — the circular base is on the ground and the height goes up. Volume is straightforward: V = πr²h.

To find the volume of liquid at a partial fill level, replace h with the liquid height: V_liquid = πr² × h_liquid.

Example: A water tank with diameter 2 m (r = 1 m) and height 3 m holds V = π × 1 × 3 = 9.42 m³ = 9,420 litres. If filled to 1.5 m, it holds 4,712 litres.

Horizontal Cylindrical Tanks

h Partial fill formula

Horizontal tanks lie on their side — the circular cross-section is vertical and the length runs horizontally. Total volume is still V = πr²L (where L is the tank length).

Partial fill is more complex. The liquid level h (measured from the bottom of the circular cross-section) gives:

V_liquid = L × [r² × arccos((r−h)/r) − (r−h) × √(2rh − h²)]

This formula accounts for the circular segment of liquid visible in the cross-section.

Tank Sizing and Capacity Planning

V W Tank capacity planning

When selecting a tank, consider usable capacity vs total capacity. Most tanks can't be filled to 100% — you need air space for expansion, ventilation, or pump suction clearance. A typical usable capacity is 80–90% of total volume.

For water storage, 1 cubic meter = 1,000 litres = 264.17 US gallons. A household pressure tank holding 200 litres needs a cylinder roughly 60 cm diameter × 70 cm tall.

Fuel tanks, septic tanks, and industrial storage all use cylindrical shapes because they distribute pressure evenly and are efficient to manufacture.

Frequently Asked Questions

How do I calculate the volume of a round tank?
Measure the inside diameter and height. V = π × (d/2)² × h. Convert to your preferred unit (litres, gallons, etc.).
How do I find the volume at a partial fill level?
For vertical tanks: V = πr² × fill_height. For horizontal tanks, use the circular segment formula, which depends on the liquid depth relative to the tank radius.
How many litres does a 1000-gallon tank hold?
1,000 US gallons = 3,785.41 litres. 1,000 Imperial gallons = 4,546.09 litres.
What size tank do I need for 5,000 litres?
5,000 litres = 5 m³. A tank with diameter 1.5 m (r = 0.75 m) and height 2.83 m would hold this volume: π × 0.5625 × 2.83 ≈ 5.0 m³.
Does tank orientation affect volume?
No. A horizontal and vertical tank with the same dimensions have the same total volume. Orientation only affects partial fill calculations and structural considerations.