Film Developing Time Calculator

Adjust your development times for temperature, film, and developer chemistry. Get consistent results at home.

Enter your actual developer temperature

Common Combinations

These are typical starting points for popular film-developer pairs at 20°C (68°F).

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Film Developer Base Time
Portra 400 Rodinal 1+50 12:00
Tri-X 400 HC-110 Dil B 10:30
FP4 Plus 125 D-76 1+1 12:00
Delta 3200 XTOL 1+1 25:00
Pro 400H T-Max RS 1+4 9:00

Temperature Adjustment Chart

Adjust times when your developer temperature differs from 20°C. For each degree below 20°C, add 8-10% to the development time. For each degree above, subtract 8-10%.

18°C+16% time
19°C+8% time
20°CBase time
21°C-8% time
22°C-16% time

Helpful Notes

Measure Accurately

Use a digital thermometer calibrated to water. Room temperature and developer temperature can differ by several degrees. Measure just before pouring developer on film.

Push Processing

Pushing increases contrast and grain. The calculator adds time based on standard formulas. For 1 stop push, typically add 50-100% to base time depending on developer.

Test Strip Method

When trying a new combination, develop a test strip of 4-6 frames with 15-second increments. This helps verify your calculated time before committing to a full roll.

Understanding the Calculations

This calculator uses Kodak's temperature compensation formulas based on the principle that development rate doubles approximately every 6°C (10°F) increase in temperature. The formulas assume: standard agitation (inversion every 30 seconds), fresh developer solution, and no pre-soak or shorter pre-soak times. Results may vary with different agitation methods, developer age, or film batch variations. Always verify with a test strip when using a new combination.

Common Mistakes to Avoid