Do I type the radius or the diameter?

Either, but tell the tool which. The field is a radius by default, and the Measure switch beside it turns it into a diameter. The diameter is the full width across the circle, which is what a tape measure gives you, and the radius is half of it. Put a diameter into the radius field by mistake and the answer comes out four times too large, because the radius is squared. When you switch to Diameter the formula line reads π r² h, r = d/2 and the working shows the halving, for example r = 1 / 2 = 0.5, so you can check which number went into the sum.

How do I get litres or gallons out of it?

They are already under the answer. Whatever unit you measure in, the tool lists litres, US gallons and UK gallons, plus three cubic units for the scale you are working at. A cylinder of radius 0.5 m and height 1.2 m is π × 0.5² × 1.2 = 0.942478 m³, and the line under the figure reads 942.478 L · 248.976 US gal · 207.316 UK gal, each repeated in full in its own row below with a Copy button. The conversions use exact definitions: a litre is 1,000 cm³, a US gallon is 231 cubic inches (3.785411784 litres) and a UK gallon is 4.54609 litres.

Can you work one through?

A drum 60 cm across and 90 cm tall, measured in metres: set Measure to Diameter, type 0.6 for the diameter and 0.9 for the height. The radius is 0.6 / 2 = 0.3 m, so the volume is π × 0.3² × 0.9 = 0.254469 m³, which is 254.469 litres or 67.2236 US gallons. In feet it works the same way: a round tank of radius 3 ft and height 4 ft is π × 3² × 4 = 113.097 ft³, which the rows give as 3,202.56 litres and 846.027 US gallons.

What about a hollow pipe?

For what a straight circular pipe holds, use Cylinder with its inner diameter and its length as Height. A 10 cm inner diameter and 300 cm length hold about 23.56 litres. This page does not accept inner and outer diameters together, compute wall material, subtract solids or model fittings and bends.

The cylinder is only part full. What do I type?

For a cylinder standing on its end, the liquid is a shorter cylinder: type the depth of the liquid as the height instead of the full height, and the volume falls in proportion, so half the height is exactly half the volume. A cylinder lying on its side is a different sum, because the liquid is a circular segment and not a shorter cylinder. Pick Tank on the shape row for that one: it takes the radius, the length and the fill depth measured up from the bottom.

Which units can I measure in?

Metres, centimetres, feet or inches, chosen on the Unit row. The volume comes back in the cube of that unit, m³ from metres and in³ from inches, with litres and both gallons underneath every time. The unit buttons change how your numbers are read rather than converting them, so if you switch from metres to feet, 0.5 becomes half a foot: retype the sides in the unit you picked.

How do I read a cylinder volume in millilitres?

One cubic centimetre equals one millilitre. Choose cm for the measured sides and the cm³ headline is the same numeric value in mL; enter dimensions measured in centimetres. The Cubic centimetres conversion row is also available when the inputs are in inches. There is no separate mL row. Use the actual perpendicular height for an oblique or slanted cylinder; a slanted axis length alone does not determine this volume.

How are measurements, units and saved work handled?

Choose the measured unit before typing; changing it reinterprets bare numbers rather than converting them. Decimal and scientific numbers, complete comma groups such as 1,200, numeric fractions such as 3/4 and mixed numbers such as 2 1/2 are accepted; written unit suffixes and expressions are not. Switching radius and diameter converts the current measurement to preserve the shape. Saved strings restore without writing defaults. Deliberate edits preserve independent newer saved fields, and malformed records are left intact. Results, full tank capacity and conversions must fit the supported numeric range. The visible result summary is selectable if the clipboard is unavailable.

Cylinder Volume Calculator

A cylinder's volume is π r² h: the area of the circular end, π times the radius squared, multiplied by the height. Type the radius and the height and the answer appears with that formula and the drawing, and the working, your numbers put in, as the first row below it. The radius is half the diameter, and the Measure switch takes whichever one you actually measured. This page opens the calculator on the cylinder whatever shape you used last, and reads the answer out in litres, US gallons and UK gallons as well as the cube of the unit you typed in.

Cylinder · π r² h0.942478m³942.478 L · 248.976 US gal · 207.316 UK gal

Shape

Measure

Radius (m)

Height (m)

Unit

A drum, can or straight pipe: use the inner radius or diameter for capacity. Height is perpendicular to the circular end, including for an oblique cylinder; it is not a slanted axis length. The drawing is schematic. Choose the measured unit before typing; changing it reinterprets the numbers.

Result summary

Cylinder, radius 0.5 m, height 1.2 m
0.942477796077 m³
The working: π × 0.5² × 1.2 = 0.942477796077 volume, in m³
Litres: 942.477796077 L
US gallons: 248.976293692 US gal
UK gallons: 207.316132342 UK gal
Cubic feet: 33.2832892609 ft³
Cubic yards: 1.23271441707 yd³
Cubic inches: 57,513.5238428 in³

The workingvolume, in m³
π × 0.5² × 1.2 = 0.942477796077
LitresL
942.477796077
US gallonsUS gal
248.976293692
UK gallonsUK gal
207.316132342
Cubic feetft³
33.2832892609
Cubic yardsyd³
1.23271441707
Cubic inchesin³
57,513.5238428

The formula is on the stage, and the working is the first row. Every answer here is one textbook formula with your numbers put in, printed so you can check it: a cylinder is π r² h, a sphere is (4/3) π r³, a pool is length times width times the average of its two depths. The horizontal tank uses the circular-segment model with stable arithmetic for a partial fill, so half way up is exactly half and a quarter of the way up is less than a quarter, because the bottom of a circle is narrow. Conversions use exact definitions: a litre is 1,000 cm³, a US gallon is 231 cubic inches and a UK gallon is 4.54609 litres. Results are rounded; drawings are schematic. No arbitrary outlines, end caps, tapered tanks, pressure, chemical dosing, reverse dimensions, subtraction or shared surface-area result is computed here.

Common questions

Do I type the radius or the diameter?: Either, but tell the tool which. The field is a radius by default, and the Measure switch beside it turns it into a diameter. The diameter is the full width across the circle, which is what a tape measure gives you, and the radius is half of it. Put a diameter into the radius field by mistake and the answer comes out four times too large, because the radius is squared. When you switch to Diameter the formula line reads π r² h, r = d/2 and the working shows the halving, for example r = 1 / 2 = 0.5, so you can check which number went into the sum.
How do I get litres or gallons out of it?: They are already under the answer. Whatever unit you measure in, the tool lists litres, US gallons and UK gallons, plus three cubic units for the scale you are working at. A cylinder of radius 0.5 m and height 1.2 m is π × 0.5² × 1.2 = 0.942478 m³, and the line under the figure reads 942.478 L · 248.976 US gal · 207.316 UK gal, each repeated in full in its own row below with a Copy button. The conversions use exact definitions: a litre is 1,000 cm³, a US gallon is 231 cubic inches (3.785411784 litres) and a UK gallon is 4.54609 litres.
Can you work one through?: A drum 60 cm across and 90 cm tall, measured in metres: set Measure to Diameter, type 0.6 for the diameter and 0.9 for the height. The radius is 0.6 / 2 = 0.3 m, so the volume is π × 0.3² × 0.9 = 0.254469 m³, which is 254.469 litres or 67.2236 US gallons. In feet it works the same way: a round tank of radius 3 ft and height 4 ft is π × 3² × 4 = 113.097 ft³, which the rows give as 3,202.56 litres and 846.027 US gallons.
What about a hollow pipe?: For what a straight circular pipe holds, use Cylinder with its inner diameter and its length as Height. A 10 cm inner diameter and 300 cm length hold about 23.56 litres. This page does not accept inner and outer diameters together, compute wall material, subtract solids or model fittings and bends.
The cylinder is only part full. What do I type?: For a cylinder standing on its end, the liquid is a shorter cylinder: type the depth of the liquid as the height instead of the full height, and the volume falls in proportion, so half the height is exactly half the volume. A cylinder lying on its side is a different sum, because the liquid is a circular segment and not a shorter cylinder. Pick Tank on the shape row for that one: it takes the radius, the length and the fill depth measured up from the bottom.
Which units can I measure in?: Metres, centimetres, feet or inches, chosen on the Unit row. The volume comes back in the cube of that unit, m³ from metres and in³ from inches, with litres and both gallons underneath every time. The unit buttons change how your numbers are read rather than converting them, so if you switch from metres to feet, 0.5 becomes half a foot: retype the sides in the unit you picked.
How do I read a cylinder volume in millilitres?: One cubic centimetre equals one millilitre. Choose cm for the measured sides and the cm³ headline is the same numeric value in mL; enter dimensions measured in centimetres. The Cubic centimetres conversion row is also available when the inputs are in inches. There is no separate mL row. Use the actual perpendicular height for an oblique or slanted cylinder; a slanted axis length alone does not determine this volume.
How are measurements, units and saved work handled?: Choose the measured unit before typing; changing it reinterprets bare numbers rather than converting them. Decimal and scientific numbers, complete comma groups such as 1,200, numeric fractions such as 3/4 and mixed numbers such as 2 1/2 are accepted; written unit suffixes and expressions are not. Switching radius and diameter converts the current measurement to preserve the shape. Saved strings restore without writing defaults. Deliberate edits preserve independent newer saved fields, and malformed records are left intact. Results, full tank capacity and conversions must fit the supported numeric range. The visible result summary is selectable if the clipboard is unavailable.

Rounded browser arithmetic for the dimensions and ideal shapes shown; pools assume a uniform or linear depth profile. Drawings are schematic. A US gallon is 231 cubic inches and a UK gallon is 4.54609 litres.