Starter feeding calculator

What a feeding ratio means

A feeding ratio is three numbers: starter, flour and water, by weight. A 1:1:1 feed is equal weights of each, say 20 g starter, 20 g flour and 20 g water. A 1:5:5 feed is 20 g starter with 100 g flour and 100 g water. Weigh everything. Spoons and cups are too rough for something this alive, and a small error in a small jar is a big one in proportion.

Before each feed, keep only what you need and discard the rest. Keeping 20 to 50 g means you throw away less, the jar stays tidy, and it is no more than a third full right after feeding, so you can see the rise clearly and nothing climbs out of the lid.

Why the ratio changes the timing

The more fresh flour you add compared with the starter, the more food there is and the more spread out the yeast and bacteria are. A small population with plenty to eat takes longer to grow and peak. So a higher ratio gives a slower, longer rise, and a lower ratio a fast, short one.

A warm kitchen speeds every one of these up, roughly by a quarter, and a cool one slows them down by about a third. These are rules of thumb, not promises. Every starter is a little different, so watch your own jar for a few days and note when it peaks at each ratio. After that, your notes beat any table.

Picking a ratio for your day

Work backwards from when you want to mix. If your starter peaks about 6 hours after a 1:2:2 feed and you want to mix at 9 am, feed at 3 am, which nobody wants to do. Feed 1:5:5 at 10 pm instead and it will be near its peak when you wake up. Change the ratio rather than your sleep.

• Baking soon, warm kitchen? 1:1:1 or 1:2:2. Quick, but it gets hungry quickly too.
• Overnight before a morning mix? 1:5:5 is the usual choice.
• Hot kitchen, or the jar has to wait all day? 1:10:10, with cooler water.
• Cold kitchen? A lower ratio and a warmer spot, around 75 to 80F (24 to 27C).

How to tell it peaked

Put a rubber band or a strip of tape on the jar at the starter's level right after you feed it. A starter at its peak has at least doubled from the band, has a domed top or one just starting to flatten, shows bubbles of many sizes down the side of the jar, and smells pleasantly yeasty and mildly sour. Once the surface sinks and leaves a streaky line on the glass above it, it has peaked and started to fall. A starter just past its peak still raises bread well. One that has sunk all the way back and smells sharply sour or like nail polish is hungry: feed it and use the next peak.

The float test is a weaker guide. A spoonful that floats is full of gas, but a stiff or whole grain starter can sink even at its peak, so a sink is only a maybe. The band on the jar tells you more.

Fridge feeding

If you bake once a week or less, keep the starter in the fridge. Feed it, leave it out for an hour or two, then refrigerate it at about 38 to 40F (3 to 4C). It can sit a week or more between feeds. Dark liquid on top after that is hooch, and it is harmless: pour it off or stir it in. The day before you bake, give it one or two feeds at room temperature until it peaks on time again. The first feed out of the fridge may not double, and that is normal.

Read more in feeding ratios explained and how to tell when your starter is ready to bake.

Sources

Ratios and peak windows are rules of thumb from the Loaf Scout app's starter guide; the rubber band method and the signs of a ripe starter follow The Perfect Loaf's starter guide; the float test's limits follow The Perfect Loaf's starter questions page; the discard and cleaning rules follow Colorado State University Extension's starter best practices. Each linked guide names its sources in full. The calculator runs in your browser and sends nothing.