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ISO Equivalence Calculator

Work out iso equivalence instantly with clear inputs, formula shown and shareable results.

About ISO Equivalence Calculator

ISO doubles per stop, so the new value is the base times two to the power of the stops; shot noise scales with the square root of the signal, so it rises by half as many stops. Each ISO stop above base typically costs about a stop of dynamic range, which is why highlight recovery collapses at high ISO even when noise looks acceptable.

Formulas

ISO change

new ISO = base ISO x 2 ^ stops

Noise

relative shot noise = 2 ^ (stops / 2)

Worked example

With the default values below, ISO Equivalence Calculator returns Equivalent ISO of 800. Change any input above and every figure here is recalculated in your browser.

Inputs used

Starting ISOminimum 1
100
Stops to pushaccepts -10–10
3

Results

Equivalent ISO
800
Relative shot noise increase
2.828 x
Approximate dynamic range lost
3.00 stops
Sensitivity multiplier
8.000 x

Step by step

  1. 1Values used
  2. 2ISO change
  3. 3Noise
  4. 4Equivalent ISO= 800
  5. 5Relative shot noise increase= 2.828 x
  6. 6Approximate dynamic range lost= 3.00 stops
  7. 7Sensitivity multiplier= 8.000 x

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the ISO Equivalence figure worked out?

new ISO = base ISO x 2 ^ stops. ISO doubles per stop, so the new value is the base times two to the power of the stops; shot noise scales with the square root of the signal, so it rises by half as many stops.

Why does this matter?

Each ISO stop above base typically costs about a stop of dynamic range, which is why highlight recovery collapses at high ISO even when noise looks acceptable.

What do I need to enter?

Enter starting iso, stops to push. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.

Related Calculators

ISO Equivalence Calculator – Calculate Equivalent ISO