Skip to content
Starter Feeding Calculator
More free tools

← Starter Feeding Calculator

Sourdough starter discard calculator

If your jar holds 300 g of starter and you want to keep 20 g, discard 280 g. At 1:5:5, add 100 g of flour and 100 g of water. Type your own jar weight in the tool below.

What do you know?

The starter left in the jar after you discard.

Weigh the jar, then subtract the empty jar. We use it to tell you how much to discard.

Feeding ratio (starter : flour : water)

1:5:5 means 1 part starter, 5 parts flour and 5 parts water, by weight.

Slower and milder. Suits one feeding a day. 1:1:1 versus 1:5:5

Your feeding

Show amounts in grams, ounces or cups

Feed 20 g starter, 100 g flour and 100 g water.

Starter
20 g
Flour
100 g
Water
100 g
Total after feeding
220 g

Discard

Keep 20 g. Discard 280 g. Add 100 g flour and 100 g water. Total 220 g.

Keep 20 g of starter in the jar and discard the rest. Then add the flour and water. Ratio 1:5:5 by weight, 100% hydration.

Rough peak time

about 8 to 12 hours

At 75 °F. A guide only: your flour, starter and kitchen will change it. Watch the jar, not the clock.

Fine-tune

100% means equal flour and water. Used with the preset ratios.

Temperature unit

Used only for the peak time guide.

Clock times (optional)

Fill in one to see clock times for the peak. Fill in both to get a ratio that fits your night.

Flour mix (optional)

White flour (all-purpose or bread): 100%

The numbers

How much to discard from a full jar when you keep 20 g or 50 g
Starter in the jarKeep 20 g: discardKeep 50 g: discard
100 g80 g50 g
200 g180 g150 g
300 g280 g250 g
500 g480 g450 g

Amounts use 100% hydration and white flour. Change hydration or the flour mix in the tool above.

How to weigh the jar

Put the empty jar on the scale and press tare. Add the starter, or weigh the jar full and subtract the empty jar. Enter the starter weight, not the jar weight.

Spoon the extra starter into a second container. Weigh the jar again to check that only the amount you want to keep is left.

Why discard at all

Without discard, the jar would grow every day and need more flour. Discarding keeps the amount of flour small and the starter fresh. A feeding of 20 g of starter at 1:5:5 uses 200 g of flour and water in total. Without discarding, a 300 g jar would need 3,000 g of flour and water.

If you do not want to waste flour, keep less starter in the jar. Ten or twenty grams is enough for many bakers.

What to do with discard

Cook with it the same day or keep it in the fridge. It makes good pancakes, waffles, crackers and flatbreads. It is fine to add fresh discard to a covered container for up to a week.

Quick answers

How much starter should I keep?

Keep as little as your routine allows. Many bakers keep 20 g to 50 g. A smaller amount means less discard and less flour, but a longer wait before the peak.

What if my jar holds less than the amount I want to keep?

Then you are short. The calculator shows how many grams are missing. Use a smaller amount to keep, or feed the jar once and wait for it to grow.

More feeding guides

More free tools from Bingemind