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Film developer dilution calculator
For a 1+9 dilution, mix one part concentrate with nine parts water. Divide the final volume by ten to find the concentrate. For 300 ml, that is 30 ml concentrate and 270 ml water.
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For 300 ml at 1+930 ml concentrate
+ 270 ml water
No minimum-capacity check: follow the manufacturer’s required concentrate per film load.
Quantities are rounded for display. Use measuring equipment accurate enough for the required amount.
A worked example
To make 300 ml at 1+9, divide 300 by 10: 30 ml concentrate plus 270 ml water. To make 500 ml at 1+4, divide 500 by 5: 100 ml concentrate plus 400 ml water. These are mixing examples, not processing recommendations for a particular film.
The formula: one part plus N parts
Concentrate = final volume ÷ (1 + water parts). Water = final volume − concentrate. The final volume is the total solution, not the amount of water you start with. Check that the volume covers the film in your tank. The calculator uses milliliters throughout.
Stock solution, concentrate and minimum capacity
Use the starting solution specified by the manufacturer. A recipe may dilute a prepared stock solution rather than the liquid from the bottle. Prepare powdered chemicals according to the manufacturer’s instructions first. Developer capacity can require a minimum amount of concentrate per roll regardless of tank volume. Enter that product-specific minimum if you know it; zero means no minimum check, not confirmation that the mix is suitable.
Proportions do not set the development time
This calculator does not select chemistry, temperature, development time, agitation or disposal instructions. Use the technical sheet for your exact developer, film and process. A more dilute solution is not automatically interchangeable. Measure accurately; very small quantities may require equipment with better resolution than a household measuring jug.
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Questions that come up
Is 1:10 the same as 1+9?
Colon notation is used inconsistently. It may mean one part in ten total parts, or one part plus ten parts. This calculator deliberately uses 1+N: one part starting solution plus N parts water. Check the maker’s notation.
Is 10 ml of concentrate always enough?
No. Minimum concentrate and capacity depend on the product and film load. A minimum mentioned in one technical sheet must not be applied to other developers.
Does the calculator adjust temperature or time?
No. It only calculates proportions. Use a verified processing recipe for time, temperature and agitation.
Can I save a timer for my recipe?
Agitate on iPhone supports film-development timing and agitation reminders. Follow the app details and your chemistry instructions when setting up a recipe.
Sources and method
The formulas and assumptions are shown above. These sources provide product instructions or context; they do not endorse this calculator.