Feeding your starter at the right time — with the right amounts — is the difference between a loaf that rises beautifully and one that goes nowhere. This calculator works in both directions: tell it when you want to mix your dough and it tells you when to feed your starter, or tell it when you’re feeding and it gives you your exact peak window. Enter your details below to get your personalised feeding schedule and ingredient amounts.
Starter Feeding Calculator
Get the exact flour, water, and timing for your next starter feed — whether you know when you want to bake, or need to work out when to feed.
We’ll add 15g extra to account for jar loss — no more scraping the jar.
Temperature adjusts your peak window — warmer kitchens speed things up significantly.
Adjusts your expected peak window based on fermentation speed.
How to Use This Calculator
This calculator has two modes depending on where you are in your planning. Use whichever fits your situation.
Mode 1 — “I Know When I’m Baking”
Use this mode when you have a target time to mix your dough — for example, you want to bake first thing in the morning and need to know when to feed your starter the night before. Enter your target mix time, how much starter your recipe needs, your feeding ratio, and your kitchen temperature. The calculator works backwards to give you an exact feed time and shows you the full timeline from feed to mix.
Mode 2 — “I Know When I’m Feeding”
Use this mode when your schedule determines your feed time — for example, you know you can feed your starter at 8pm and want to know what time it will peak. Enter your feed time, starter amount, ratio, and kitchen temperature. The calculator gives you your peak activity window and a “use before” time so you know exactly how long you have before your starter passes its peak.
Feeding Ratio
The ratio controls how long your starter takes to peak. A 1:1:1 ratio (equal parts starter, flour, water) peaks fastest — in 4–6 hours. A 1:5:5 ratio (one part starter to five parts each of flour and water) peaks slowly — in 10–14 hours. Higher ratios are useful in warm kitchens or when you need more lead time. For a deeper explanation of how ratios work, read our complete sourdough starter guide.
Kitchen Temperature
Temperature is the most misunderstood variable in starter timing. At 80°F, your starter can peak in half the time it would at 65°F. The calculator adjusts your peak window based on your actual kitchen temperature — always use your real temperature, not an assumed 70°F, for accurate results.
Starter Amount
Enter the amount your recipe calls for. The calculator automatically adds 15g to account for what sticks to the jar and spoon — so you always have enough without scraping the jar clean before mixing.
How to Read Your Starter at Peak
The peak window the calculator gives you is when your starter is at its most active. But numbers are only a guide — always confirm with your eyes before mixing. Your starter is at peak when:
- It has at least doubled in volume since feeding
- The top is domed, not flat or sunken
- It is full of bubbles throughout — not just at the edges
- It passes the float test — a small spoonful dropped in water floats
- It smells yeasty and tangy, not sharply sour or like alcohol
If your starter has peaked and sunken before you are ready to mix, do not use it. Feed it again and wait for the next peak. Using a starter that has passed peak is one of the most common reasons for dense, under-risen sourdough — no amount of good technique compensates for an exhausted starter.
What the Timeline Shows
The three-point timeline — Feed, Peak Window, Mix or Use Before — gives you your complete action plan. The “Use Before” time in Mode 2 is two hours after the end of your peak window. This is a conservative buffer — using your starter right at or just past peak can still work, but results become less reliable as it moves toward exhaustion.
Why the Calculator Adds 15g Extra
Every time you scoop starter from a jar, some stays behind on the sides, spoon, and bottom. Over the course of a feed and a mix, this adds up to more than most bakers account for. The 15g buffer means you will always have exactly what you need in the bowl — not a stress-inducing shortage when you are mid-recipe. Keep the extra in the jar as your carry-over for the next feed.
Frequently Asked Questions:
How do I know what feeding ratio to use?
Base your ratio on your schedule, not a preference. If you need your starter ready in 4–6 hours, use 1:1:1. If you are feeding before bed and want to mix in the morning, use 1:2:2 or 1:3:3. If your kitchen is warmer than 76°F, use a slower ratio like 1:3:3 or 1:5:5 to stop it peaking while you are asleep. Let your timeline decide the ratio — not the other way around.
Can I feed my starter straight from the fridge?
Yes, but expect a longer rise time. Cold starter takes longer to reactivate because the yeast and bacteria are sluggish after refrigeration. Either let it come to room temperature for 30–60 minutes before feeding, or simply add extra time to your peak window. After a week or more in the fridge, consider doing a discard-and-feed cycle first before your bake feed to wake it up fully.
What if my starter peaks earlier or later than the calculator predicts?
This is normal — the calculator gives you a window based on averages, but your specific starter culture, flour type, and exact temperature all affect timing. Over time you will develop a feel for how your starter behaves. Use the calculator as your starting point and adjust the ratio up or down by one step on your next bake if timing is consistently off.
How much starter should I keep after feeding?
Most home bakers keep 20–50g of starter as their carry-over. Keeping less is not a problem — a smaller amount of healthy starter will grow just as well as a larger amount. The main reason to keep it small is to reduce the amount of discard you produce each feed. If you bake regularly (more than twice a week), keeping 30–50g is practical. If you bake less often, keep it in the fridge and feed once a week.
Does the type of flour I feed my starter affect the timing?
Yes, significantly. Whole wheat and rye flours contain more wild yeast and bacteria than white flour, so a starter fed with whole grain flour will peak noticeably faster. Rye in particular is known for accelerating activity. If you switch flour types, expect your peak window to shift and use the calculator as a guide while you recalibrate over the next two or three feeds.
My starter doubles but my bread is still dense — what’s wrong?
Doubling is a necessary condition but not a sufficient one. Your starter also needs to be used at the right moment — at or near its peak, not after it has collapsed. A starter that doubles in 12 hours is significantly weaker than one that doubles in 4–6 hours. If your starter is very slow, consider more frequent feedings over 3–5 days to strengthen it before your next bake. For a full guide to diagnosing starter problems, read our article on sourdough starter not rising.