Ratio is always starter : flour : water by weight. Change it live in the calculator below.
Live calculator · updates as you type
Your feed
g
100%
50%100%200%
Feeding ratio (starter : flour : water)
Feed with
Flour to add67g
Water to add67g
Starter used67 g
Total after feeding200 g
Starter Flour Water
Discard
Keep in jar67 g
→
Discard133 g
Don't bin it — discard is great for pancakes, crackers, and pizza dough.
Estimated peak4–6h
At 24°C (75°F) with ratio 1:1:1 and 100% hydration. Peak is when the starter domes at its highest and is covered in bubbles — use it at peak for the most lift.
Feeding ratio reference — at 24°C (75°F)
Ratio (S:F:W)Peak timeFlavour profile
1:1:13–5hMild, fast — great for daily bakers
1:2:25–8hBalanced, versatile
1:3:37–10hSlightly more sour
1:5:510–14hMore sour, good for overnight
1:10:1016–20hVery slow, strong acid development
Times vary with kitchen temperature, flour type, and starter health.
Results use baker's percentages. Flour and water amounts are relative to the total starter weight you need. Hydration sets the flour-to-water balance inside the starter itself.
Sourdough starter guide
Feed precisely. Bake consistently.
Starter health is the foundation of every sourdough loaf. Getting the ratio and hydration right means predictable peak times, consistent dough behaviour, and bread you can reliably repeat.
Daily feeding1:1:1
Equal parts starter, flour, water. Peaks in 3–5h at 24°C.
Overnight1:5:5
More dilution, slower peak. Feed at night, bake in the morning.
Standard hydration100%
Equal weights flour and water. Most recipes assume 100%.
Key ratio ruleS : F : W by weight
A 1:2:2 ratio means for every 1g of starter you keep, you add 2g flour and 2g water. Total parts = 5, so each gram is 1/5th of the finished weight.
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How to use this sourdough starter calculator
Enter the total weight of starter you need for your recipe — this is the number you see in the ingredients list (e.g. 200g active starter). Then set your feeding ratio using the preset buttons or choose Custom to enter any ratio. Finally, set your starter hydration and adjust your jar size to see exactly how much to discard.
The calculator outputs the flour and water to add, the amount of existing starter to keep, and a discard amount based on your jar size. Change any input and all values update instantly. There's no need to do the arithmetic yourself.
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What is a sourdough starter?
A sourdough starter is a live culture of wild yeast and lactic acid bacteria maintained in a mixture of flour and water. Unlike commercial yeast, which is a single strain bred for reliability and speed, a sourdough starter is an ecosystem. Wild yeasts produce carbon dioxide to leaven bread; bacteria produce lactic and acetic acids that give sourdough its distinctive tang.
Maintaining a starter means feeding it regularly — discarding a portion and adding fresh flour and water to keep the culture healthy and active. The ratio at which you feed, the flour you use, and the temperature of your kitchen all affect how fast the starter peaks and how it behaves in a recipe.
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Understanding feeding ratios
A feeding ratio like 1:2:2 is always written as starter:flour:water by weight. The first number is the portion of existing starter you keep; the second and third are the flour and water you add. A 1:1:1 ratio is the most common for daily maintenance — it's fast (peaks in 3–5 hours at 24°C) and keeps the starter active. Higher ratios like 1:5:5 dilute the culture more, slow fermentation, and can push the peak to 10–14 hours, which suits overnight schedules.
The ratio also affects flavour. Lower ratios (1:1:1 or 1:2:2) produce a milder, more lactic starter because the bacteria don't have as much time to produce acetic acid. Higher ratios give the bacteria more time and can produce a more sour, acetic profile. If you want a mild, milky loaf, stick with 1:1:1. If you want a more complex tang, use 1:5:5 or even 1:10:10.
Ratio quick reference at 24°C (75°F)
1:1:1 → peak in 3–5h, mild flavour1:2:2 → peak in 5–8h, balanced1:5:5 → peak in 10–14h, more sour1:10:10 → peak in 16–20h, strong tang
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How starter hydration affects your bread
Starter hydration is the ratio of water to flour in your starter by weight, expressed as a percentage. A 100% hydration starter has equal weights of flour and water — it's pourable, active, and peaks quickly. A 65–75% hydration starter is a soft dough consistency; a 50% hydration starter is stiff and often used in Italian baking (lievito madre).
Higher hydration starters tend to favour lactic acid production (milder, yoghurt-like) because the wetter environment suits lactobacillus bacteria. Stiffer starters favour acetic acid production (sharper, vinegary), which is why stiff starters are used in very sour breads. Hydration also affects how much water you're adding to your final dough — if your recipe uses 150g of 100% hydration starter, that's 75g flour and 75g water you need to account for in your overall dough formula.
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What to do with sourdough discard
Discard is the portion of starter you remove before feeding. You must discard to keep the culture in balance — if you never remove any, the growing starter eventually produces so much acid that it inhibits its own yeast. But discard doesn't need to go in the bin. It's simply unfed starter — still alive, still useful, just past its peak.
The most popular use for discard is pancakes. Replace some of the milk and flour in your favourite pancake recipe with an equal weight of starter discard. You'll get a slight tang and exceptional tenderness. Other uses: sourdough crackers, pizza dough, English muffins, flatbreads, banana bread, and muffins. Keep a jar of discard in the fridge and top it up each time you feed your main starter.
06Readiness check
How to know when your starter is at peak
Peak is the moment when your starter has risen as high as it will go and is covered in bubbles. It's the ideal time to use it in a recipe because the yeast activity is at its strongest and the acidity is in a good range. Using starter past peak can result in over-acidified dough that's difficult to shape and bakes to a flat loaf.
The best way to track peak is with a rubber band on your starter jar. Mark the level right after feeding and check it every hour. When the starter stops rising and the dome just begins to flatten, it's at peak.
VolumeStarter has doubled (or more) from the level right after feeding.
SurfaceDomed top covered in small bubbles, sides showing bubble tracks.
SmellYeasty and mildly tangy — not sharp, alcoholic, or acetone-like.
Float testA small spoonful dropped in water should float.
FeelLightly airy when you stir it — not dense or batter-thick.
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Troubleshooting a sluggish starter
If your starter isn't doubling reliably, the most common causes are low temperature, poor-quality flour, and infrequent feeding. Temperature is usually the first thing to check. Below 18°C, wild yeast activity slows dramatically. Move the starter somewhere warmer — on top of the fridge, near the oven, or in an oven with only the light on. Even a 3–4°C increase makes a measurable difference.
Flour quality matters more than most bakers expect. Try adding 10–20% whole wheat or rye flour to your feeding mix for two or three cycles. The bran carries native yeast and bacteria and tends to accelerate activity in a sluggish culture.
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Storing your starter between bakes
If you bake once a week or less, keep your starter in the fridge between bakes. Feed it before putting it in, let it rise for an hour or two at room temperature, then refrigerate. A cold, well-fed starter can last 1–2 weeks without attention. Before your next bake, take it out, let it come to room temperature for an hour, then feed it once or twice to wake it up.
Some bakers dry their starter as a backup. Spread a thin layer on parchment, let it dry at room temperature for 24–48 hours, break it into flakes, and store in an airtight jar. Dried starter keeps for years.
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Worked examples: starter maintenance math
Two numbers drive every feed: how much starter you want, and your feeding ratio (starter:flour:water by weight). Working backwards from the total keeps you from over- or under-building. Each feed multiplies your kept starter by the sum of its parts — a 1:4:4 feed multiplies by 9 (1 + 4 + 4), so keeping 25g and adding 100g flour + 100g water yields 225g.
For a recipe calling for 200g of 100% hydration starter plus a little to carry forward, keep about 30g and feed 1:4:4 (120g flour + 120g water) to make roughly 270g — 200g for the dough, ~70g to keep the culture going. Remember that 200g of 100% starter contains 100g flour and 100g water, which you subtract from your final dough formula so the loaf hits its target hydration.
Maintenance math at a glance
Total = kept × (1 + flour parts + water parts)1:1:1 from 50g → 150g total1:4:4 from 25g → 225g totalNeed 200g? keep ~30g and feed 1:4:4
Download the free Sourdough Baking Playbook
Get the complete Sourdough Baking Playbook — starter ratios, hydration, levain builds, bulk timing, and discard in one printable reference.
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Free Sourdough Baking Playbook (printable PDF)
FAQ
Sourdough starter questions
Common questions about ratios, hydration, and discard.
What does 1:1:1 feeding ratio mean?
A 1:1:1 ratio means equal parts existing starter, flour, and water by weight. If you have 50g of starter, you add 50g of flour and 50g of water, giving you 150g total. It's the most common ratio for daily maintenance because it's simple and keeps the starter active with a peak time of around 3–5 hours at room temperature.
How do I calculate how much flour and water to add?
To feed your starter, divide the total starter weight you need by the sum of your ratio parts. For a 1:2:2 ratio, the total parts are 1+2+2=5. If you need 250g of fed starter, each part is 250/5=50g. So you keep 50g of starter, add 100g of flour and 100g of water. This calculator does that arithmetic automatically.
What is starter hydration and how does it affect baking?
Starter hydration is the ratio of water to flour in the starter, expressed as a percentage. A 100% hydration starter (equal weights of flour and water) is a pourable, pancake-batter consistency. A 50% hydration starter is a stiff dough. Higher hydration starters tend to peak faster and develop more lactic (milder, yoghurty) acidity. Stiffer starters often develop more acetic (sharper, vinegary) acidity and can be more forgiving in warm kitchens.
How much discard should I remove?
Discard is the portion of your existing starter you remove before feeding. If you never discard, your starter jar would grow exponentially and the pH would drop so low the culture becomes inhibited. Typical practice is to keep only what you need for the next feeding plus a small buffer — usually 20–50g. This calculator lets you set your jar size and tells you exactly how much to discard.
When is sourdough starter ready to use?
Your starter is ready to use when it has doubled in size, domes at the top, and is covered in bubbles. The classic test is the float test: drop a small spoonful into a glass of water — if it floats, the starter has enough gas to leaven bread. The timing from feeding to peak depends on your ratio, temperature, and flour type. At 24°C with a 1:1:1 ratio, most healthy starters peak in 3–5 hours.
What is the difference between starter and levain?
A starter (also called a mother starter or chef) is the ongoing culture you maintain and feed regularly. A levain (or pre-ferment) is a portion of starter mixed with fresh flour and water specifically to use in a recipe — it's built to peak at baking time and is separate from your main jar. The levain calculator handles the levain-specific calculation; this calculator handles the ongoing feeding of your main starter jar.
How much does temperature change starter peak time?
A lot — temperature is the biggest single factor. Holding a 1:1:1 ratio, a starter peaks in about 4–6 hours at 24°C / 75°F, 8–10 hours at 20°C / 68°F, and just 2–4 hours at 28°C / 82°F. Roughly, every 4°C / 7°F change halves or doubles the time. If yours is peaking too fast or too slow, adjust where the jar sits before changing anything else.
Why is my sourdough starter not rising?
The usual causes are cold, hunger, or excess acid. Move it somewhere warmer (24–28°C), feed it twice a day at 1:1:1, and discard down to 20–30g so acid doesn't build up. Adding a little whole wheat or rye to the feed reboots a sluggish culture. A young starter under two weeks old also naturally goes quiet after an early false rise — keep feeding through it.
Can I feed my starter without discarding?
Not indefinitely. If you never discard, the jar grows exponentially and the acidity climbs until it inhibits the yeast, so the starter weakens. You can skip discarding for a feed or two if you're deliberately building up volume for a big bake, but for routine maintenance keep only 20–50g and feed that. Save the discard for pancakes or crackers rather than binning it.
