Rule of 240

The Journey

In my bread making journey I have discovered that making bread is incredibly easy and yet incredibly complex at the same time. There are scientific principles that govern each step of the baking process. Of course we all know that baking is a skill that requires a lot of precision and there are rules of physics that govern each step precisely.


The first thing we learn is that all components in every baking project must be measures precisely in some way in order for the resulting baked good to be satisfyingly good when completed.

We then learn that measuring your dough by using a scale to weigh it is gives us much better results, that are consistent and repeatable. It also makes it much easier to duplicate someone else’s recipe without experiencing failure.


The next step is to learn how to adjust the temperature of the water so our yeast is sufficiently active to give us consistent results.

I knew that making the water temperature hotter would result in much more yeast activity. In multiple experiments I found that I could really wake up a recipe and produce a light fluffy loaf of bread by using hot water but then sometimes that same exact method would result in a loaf of bread that would over-inflate and collapse. There was obviously a consistency problem but I didn’t know why.

Searching the internet came up with a lot of information for professional bakers which looked interesting and promising but I was simply teaching myself how to make bread at home. Something simpler was needed. I kept searching.

That is where The Rule of 240 comes in. It tells us what temperature to set our water to (I never use tap water, chlorine, chloramine and possibly other treatments in it can kill off yeast) a temperature that yields a final dough temperature that is amenable to our yeast.

Professional bakers call this Desired Dough Temperature (DDT). I’m sure that calculating DDT at home would work but I wanted something simple that I could start with. I could upgrade to DDT at a later time if I felt the need to do so. So far (after several years of baking bread), the Rule Of 240 works very well for me so I’m sticking with it.

The Rule Of 240

Water temperature = 240 minus (Room Temperature + Flour Temperature)

Ensure that the water temperature does not exceed 120 degrees F (yeast will completely die off by 130 degrees F)

This gives you a reasonable starting point. After you have baked a few successful loaves, you may adjust your water temperature differently to make your final loaf exactly as you desire it to be, but the Rule Of 240 will definitely get you very close to perfect.

An example of the Rule of 240 in action:

It is 73 degrees F in my kitchen right now. My flour is 69 degrees F so I add the two together to get 142.

Then I calculate 240 minus 142 and get 98.

This means that my water temperature needs to be 98 degrees F for this specific dough.

Sourdough – Preferment

The Rule Of 320 is applicable when using sourdough starters or preferments. The temperature of the sourdough (preferment) is added to the temperature of the flour and the room temperature. Subtract  this total from 320 to arrive at the water temperature.


Enjoy your bread, Thank you for your support, Please don’t forget to visit the sponsors of my site, like Amazon it doesn’t cost you anything at all and the modest commission I receive helps defray the cost of running my DrBobTechBlog website.

Dr Bob