Developer dilution calculator
Mixing chemistry at 1+9, 1:25, 1:50? Get the exact concentrate and water.
Tip: a standard 35mm tank needs ~300ml, a 120 tank ~500ml, two 35mm ~600ml.
About this tool
Mixing a working solution from concentrate is just ratios, but it is easy to slip in the dark. Enter the dilution ratio, such as 1+31, and the total working volume you need. The calculator returns exactly how much stock developer and how much water to combine, so every batch is repeatable.
How to use it
- Enter the dilution ratio as stock plus water, for example 1+31 or 1+9.
- Enter the total working volume your tank needs, in millilitres.
- Read the amount of stock developer and water to measure out and mix.
FAQ
What does a ratio like 1+31 mean?
It means one part stock developer to 31 parts water, giving 32 parts total. For 640 ml of working solution that is 20 ml of stock and 620 ml of water. The plus sign format avoids the confusion of 1:31 versus 1 in 31.
How much working solution do I actually need?
Match your tank and reel capacity, and check the minimum stock the developer needs per roll. Some highly diluted developers require a floor of concentrate per film to develop fully, so mix a little extra rather than too little.