r? • Reviewed 2026-11-05

Find Cylinder Radius From Volume and Height

Solve the inverse cylinder formula when volume and perpendicular height are known.

Quick answer

The short version

Divide volume by πh and take the positive square root: r = √(V/(πh)).

r = √(V ÷ (πh))

Interactive tool

Calculate without radius

Values convert through SI units; displayed digits are rounded only at the end.

r = √(V/(πh))

r h
Derived dimension
—cm

Complete the fields to calculate.

How the result changes

Calculated from the current dimensions
How the result changesComplete the calculator to display a graph.
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Checked example

Worked calculation

Result: Volume 603.185789 cm³ and height 12 cm give r = √(603.185789/(12π)) = 4 cm.

01 • Guide

Use the positive root

Algebra produces a squared radius, but physical radius is nonnegative. A positive volume and height yield one positive radius; negative dimensions have no geometric meaning.

Keep the full precision of intermediate values and round only the final display. This avoids compounding error when a derived radius or converted unit is used in another step.

02 • Guide

Other routes to radius

Diameter gives r = d/2, circumference gives r = C/(2π), and base area gives r = √(A/π). Choose the directly measured quantity with the best accuracy.

The calculator validates physical limits before displaying a result. Blank or impossible inputs never produce a stale value, NaN or Infinity.

03 • Guide

Round-trip verification

A useful check is to substitute the derived radius back into πr²h. It should recover the original volume within floating-point and measurement tolerance.

Interpretation

How to use the result responsibly

The answer models an ideal geometric cylinder. Manufacturing tolerances, wall thickness, rounded ends, deformation, tank tilt and measurement uncertainty can all shift a real value. Use inside dimensions for capacity and outside dimensions for occupied space. For safety, compliance, dosing, structural or purchasing decisions, compare the estimate with drawings, calibration data or a qualified professional.

Dimensional checks help catch mistakes: a volume result must carry cubic units, an area result square units and a derived radius or height linear units. If changing one unit alters the represented physical size, a conversion step was missed.

Clear answers

Without radius: common questions

Can height alone determine radius?

No. A volume, area, circumference or diameter is also required.

Why is there a square root?

Because radius appears squared in the original volume formula.

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