The formula, and why it multiplies
Water temperature = (target dough temperature × number of terms) − (flour + room + preferment + friction). The number of terms is three without a preferment and four with one, and it is not arbitrary: you are averaging that many contributions, so the target has to be scaled up by the same count before the known ones are subtracted.
A worked case. Target 78 F, flour at 70, room at 72, friction 24, no preferment. Three terms, so 3 × 78 = 234, minus 70 + 72 + 24 = 166, leaves water at 68 F. Add a levain at 72 and it becomes four terms: 4 × 78 = 312, minus 70 + 72 + 72 + 24 = 238, leaves 74 F. The levain being close to the target pulls the required water up, which is the sort of thing that is obvious afterwards and never before.
Friction is the term nobody measures and everybody guesses
Friction factor is how much the mixing itself warms the dough. It is not a property of the recipe or of the flour. It is a property of your machine, your mix time and your speed, and the spread across equipment is enormous — a slow hand mix adds a couple of degrees, a spiral mixer on a long final speed adds well over twenty. Guessing it wrong puts the error straight into the water temperature at full size, which is why every other refinement in this calculation is pointless until it is measured.
Measuring it takes one batch. Mix as you normally would, note the water temperature you used, and probe the dough at the end of mixing. Then friction = (terms × actual dough temperature) − (flour + room + preferment + water). Do that once and write it on the mixer. Redo it if you change mix time, speed or the size of the batch, because all three move it.
Ice, and why so little of it does so much
Melting ice absorbs about 144 BTU per pound before the meltwater warms by a single degree, against 1 BTU per pound per degree for liquid water. So swapping part of the water for ice is a far stronger lever than chilling the water in the fridge. The split works out as ice = total water × (tap temperature − target water) ÷ (112 + tap temperature), with everything in Fahrenheit.
| Tap at | Water wanted | Ice, out of 350 g | Tap water |
|---|---|---|---|
| 60 F | 50 F | 20 g | 330 g |
| 60 F | 40 F | 41 g | 309 g |
| 75 F | 50 F | 47 g | 303 g |
| 75 F | 40 F | 66 g | 284 g |
Two practical points. The ice is part of the formula water and not an addition to it, or the dough comes out wetter than the formula says. And ice that has not melted by the end of mixing has not transferred its heat, so it wants to go in with the water at the start rather than being dropped on top of a developed dough.
What the calculation cannot rescue
If the answer comes out below freezing, no amount of ice fixes it, because a water and ice slurry sits at 32 F and stops. That result means the flour, the room or the mix is contributing too much heat for the target, and the usual response is to chill the flour — every degree the flour comes down takes a degree off the water temperature the formula asks for. In a hot kitchen in August, bakers routinely refrigerate flour overnight for exactly this reason.
Nothing on this page suggests what dough temperature to aim for. That is a decision inside your own formula, and it interacts with fermentation in ways no calculator should be prescribing. What this does is hit the number you already chose. For the rest of the formula, the bakers percentage calculator handles percentages and weights, the levain build calculator deals with a preferment as a temperature term and as flour and water, and the oven temperature converter covers the other end of the day.
Questions people ask
What water temperature do I need for a 78 F dough?
Multiply 78 by the number of temperature terms and subtract the ones you know. Without a preferment that is three terms: 3 × 78 = 234, minus the flour temperature, the room temperature and the friction factor. With flour at 70, a room at 72 and friction of 24, the water comes out at 68 F. Change any of those and the water moves one degree for each degree they move, which is the whole reason the water is the ingredient you adjust.
What is a friction factor and how do I find mine?
It is the temperature rise the mixing itself puts into the dough, expressed in degrees. Find it by measuring one batch: mix normally, note the water temperature you used, and probe the dough when mixing finishes. Then friction = (number of terms × the dough temperature you got) − (flour + room + preferment + water). A hand mix is usually a few degrees. A spiral mixer on a long mix can be twenty-five or more. It is not transferable between machines and it moves if you change mix time or speed.
Do I use three or four in the formula?
Three when the mix is flour, water and salt with no preferment, and four when a levain, poolish or biga is going in, because that is one more temperature contributing to the average. Some bakers use a fifth term for a very large amount of another ingredient at a known temperature, such as a big addition of milk or soaker. The rule is simply that the multiplier equals the number of temperatures you are subtracting, friction included.
How much ice should I use to cool the water?
Ice = total water × (tap temperature − water temperature you want) ÷ (112 + tap temperature), in Fahrenheit. For 350 g of water at 60 F tap and a 45 F target that is 350 × 15 ÷ 172, about 31 g of ice and 319 g of tap water. Weigh the ice as part of the formula water rather than adding it on top, or the dough comes out wetter than intended, and get it in at the start of the mix so it has time to melt.
The calculator says I need water below freezing. What now?
It means the flour, the room and the mixer between them are already contributing more heat than the target allows, and cooling the water cannot make up the difference because liquid water stops at 32 F. Chilling the flour is the usual fix, and it is a one-for-one trade: every degree off the flour is a degree back on the water the formula asks for. Shortening the mix, dropping the mixer speed, or mixing a smaller batch all reduce the friction term as well.