Equatara
Menu

physics calculator

Aperture Area Calculator

Calculate the geometric area of a circular aperture from its diameter or radius.

Aperture Area Calculator

Aperture area

Choose diameter or radius and enter a value.

Formula version 1.0.0

How to use this calculator

  1. Choose whether the known measurement is diameter or radius.
  2. Enter the positive measurement.
  3. Select Calculate.
  4. Read the circular area in square input units and inspect A = πr².

Symbols and units

SymbolMeaningUnit or domain
dAperture diameterLength
rAperture radiusLength
ACircular aperture areaSquare length
πCircle constantUnitless

Checked examples

Diameter known

Inputs: Diameter 10

Calculation: r = 10 ÷ 2 = 5; A = π×5²

Result: 25π ≈ 78.5398 square units

Diameter is halved before applying the area formula.

Check: aperture-area.test.ts

Radius known

Inputs: Radius 5

Calculation: A = π×5²

Result: 25π ≈ 78.5398 square units

The same opening gives the same geometric area.

Check: aperture-area.test.ts

Assumptions, rounding, and limits

  • The aperture is a perfect circle.
  • The input is positive.
  • The result uses square input units.
  • Vignetting, transmission, f-number, and optical throughput are not modeled.

Frequently asked questions

Is diameter the same as radius?

No. Diameter is twice the radius.

Does this calculate f-number?

No. F-number also requires focal length.

Is this the effective light-gathering area?

It is geometric area only; obstructions and transmission losses can reduce effective throughput.

Sources and review

Formula version
aperture.area@1.0.0
Formula review
Equatara formula review
Editorial review
Equatara editorial review
Last verified
2026-10-25
Applicability
Geometric area of an ideal circular aperture.
Next review
On material formula/source change, or by 2028-10-25.

Found a problem?

Report a formula, result, example, source, or accessibility issue through the calculator correction process. Do not include sensitive input values.