Toolminex
⬡
Tank Diagram
—HEIGHT—RADIUS—DIAMETER—

Height

—

Radius

—

Diameter

—

Volume

—

Not to scale · updates live

Result

Enter radius (or diameter) and height to see the result.

How to calculate the volume of a cylindrical tank

You need two measurements, the width across and the height, both in the same unit.

  1. 01

    Pick the unit you measured in

    The dropdown covers mm (the default), cm, m, km, inches, feet and yards. Radius, diameter and height all use the same unit, so measure everything the same way.

  2. 02

    Enter the inside radius or diameter

    Fill in either one and the other updates itself. Measure inside the wall if you can. Outside measurements include the wall thickness and overstate how much the tank holds.

  3. 03

    Enter the height and read the capacity

    The result shows litres and cubic metres, worked out with V = π × r² × h. A tank 1 m across and 1.5 m tall holds 1,178 L, or 1.18 m³.

Capacity of common tank sizes

Use this to sanity-check a brochure or a result. Each cell is π × (diameter ÷ 2)² × height, converted to litres and rounded to the nearest litre.

Inside diameter1.0 m tall1.5 m tall2.0 m tall
0.6 m283 L424 L565 L
0.8 m503 L754 L1,005 L
1.0 m785 L1,178 L1,571 L
1.2 m1,131 L1,696 L2,262 L
1.5 m1,767 L2,651 L3,534 L
2.0 m3,142 L4,712 L6,283 L

Notice how diameter dominates. Going from 1.0 m to 2.0 m across quadruples the capacity at any height, because the radius is squared. Adding height only grows it in a straight line.

Two worked examples

A standard steel drum is about 572 mm across inside and 851 mm tall. Enter 572 as the diameter and 851 as the height in mm, and you get 218.68 L. That's why a drum sold as "200 litres" or "55 gallons" holds a little more than its label when filled to the brim.

Pipes work the same way, lying down. 100 m of pipe with a 50 mm bore holds π × 0.025² × 100 = 0.196 m³, or 196 L of water. Enter the length as the height. It's a useful figure when you're draining a system or dosing it with antifreeze.

Where cylinder volume comes up

Rooftop and underground water tanks

Check whether the tank you've got matches what the dealer said it holds, before you plan water use around it.

Rain barrels and harvesting drums

Measure a drum you already own to see how many litres one good downpour can fill.

Concrete columns and sonotubes

A round column 300 mm across and 3 m tall needs 0.21 m³ of concrete. Order a little extra for waste.

Draining a heating loop

Measure the pipe runs and add them up, so you know how much water or glycol will come out and go back in.

What the volume calculator assumes

  • It treats the tank as a straight cylinder with flat ends. Domed or cone-bottom tanks hold a bit more or less, so add the end sections separately.
  • It gives full capacity only. For a horizontal tank part-filled to a certain depth, the maths is different and this tool won't do it.
  • Results are in litres and cubic metres. For US gallons, divide litres by 3.785 or use the Volume Converter: 1,178 L is 311.2 gallons.
  • Answers are rounded to two decimal places, with very small cubic-metre values shown to four.

Frequently asked questions

V = π × r² × h, where r is half the diameter. With the diameter it's π × d² × h ÷ 4, which gives the same answer.
When full, yes. Orientation changes how the level relates to the volume, not the total. Enter the length of a horizontal tank as the height.
Divide the circumference by 2π (about 6.283). A tank 3.77 m around has a radius of 0.6 m, so a 1.2 m diameter.
No. The calculation runs in your browser as you type, and nothing is sent anywhere.

Related cylindrical tools

Something not working right?