Film Developing Time Calculator:

This calculator takes a standard developing time and adjusts it for temperature. To use it, obtain your nominal developing time and temerature from either your official datasheet for the developing process, or from the Massive Dev Chart and enter the values into the boxes below, along with the current temperature. You can also indicate whether you will be constantly agitating the developer, which reduces the developing time. I have (at the moment) a constant reduction of 10%. Then submit, and the results should give you at least an approximate time. Please note though, that this is only valid for Ilford B&W film/developer. Results may vary for other combinations. The output will also include warnings if the difference between nominal and actual temperature is large, or the final developing time is short.

Set parameters:

Fill in the fields below. Invalid numbers will be truncated, and all will be rounded to two decimal places.

Nominal Temperature: the temperature you are supposed to be developing at: e.g., 20C for Ilford.

Nominal Time: the developing time at the nominal temp (in minutes).

Actual Temperature: the actual temperature you are developing at.

The temperature units (default is Celsius)

Will you be agitating constantly? (-10% developing time if yes)


Actual development time = 10 minutes and 0 seconds.


Further Information:

This calculation is based on times given in the Ilford data sheets, e.g. see here or here.

Other films might have different times, and some data exists, but has not been included into this yet, e.g. see here or here.

For some more information see this

Essentially this uses an exponential factor, i.e.,

\[ t_{actual} = t_{nominal} e^{ \alpha (T_{nominal} - T_{actual} ) }\]

Where \( \alpha \) was determined from the Ilford data sheet (and big T refers to temperature, and little t refers to times).


Page written by Matthew Roughan