Sourdough Starter Percentage: How Much Starter Should You Use?
Starter percentage (also called inoculation or levain percentage) is the weight of starter relative to the flour in your dough. Here's how to calculate it and how changing it affects your bake.
The formula
starter weight = flour weight × starter % ÷ 100
And the other way round: starter % = starter weight ÷ flour weight × 100. For example, 100 g of starter with 500 g of flour is 20%. The calculator uses this convention: starter as a percentage of the flour you add to the bowl.
Gram table
| Starter % | 500 g flour | 1 kg flour | 1 lb flour (453.6 g) |
|---|---|---|---|
| 5% | 25 g | 50 g | 22.7 g (0.8 oz) |
| 10% | 50 g | 100 g | 45.4 g (1.6 oz) |
| 15% | 75 g | 150 g | 68.0 g (2.4 oz) |
| 20% | 100 g | 200 g | 90.7 g (3.2 oz) |
| 25% | 125 g | 250 g | 113.4 g (4 oz) |
| 30% | 150 g | 300 g | 136.1 g (4.8 oz) |
How much is normal?
Many home sourdough recipes use somewhere between 10% and 30%, and 20% is a very common default. Same-day recipes sometimes go higher. As a general pattern:
- More starter means faster fermentation, so bulk fermentation finishes sooner.
- Less starter means slower fermentation. That's useful in a warm kitchen, or when you want a long, easy-to-manage bulk.
- Temperature matters as much as quantity. Many bakers use less starter in summer and more in winter to keep timings similar.
Flavour also changes with time and temperature, not just with the amount of starter, so there is no single "right" percentage. Pick one, keep notes, and change one thing at a time.
Three conventions you'll see in recipes
- Starter as a % of the added flour. The most common in home recipes, and what this calculator uses. 100 g starter + 500 g flour = 20%.
- Starter as a % of total flour, counting the flour inside the starter. With a 100% hydration starter: 100 ÷ (500 + 50) = 18.2%.
- Prefermented flour %. Only the flour inside the starter, as a share of all flour: 50 ÷ 550 = 9.1%. Some bakers prefer this because it doesn't depend on starter hydration.
If a recipe's numbers look odd, check which convention it uses before changing anything.
Starter hydration changes the split
The flour in a starter = starter weight ÷ (1 + starter hydration). The rest is water.
- 100 g of a 100% hydration starter = 50 g flour + 50 g water.
- 100 g of a 50% hydration (stiff) starter = 66.7 g flour + 33.3 g water.
- 100 g of a 125% hydration starter = 44.4 g flour + 55.6 g water.
So swapping a liquid starter for a stiff one at the same weight makes the dough slightly drier. Enter your starter's hydration in the calculator and the true hydration updates. The 80% hydration guide walks through a full example.
Feeding ratios vs starter percentage
A feed of 1:1:1 (starter : flour : water by weight) and a feed of 1:5:5 both give a 100% hydration starter. The ratio changes how long it takes to peak, not its hydration. Starter percentage is about the dough: how much of that ripe starter goes into the bread.
Try different starter percentages and starter hydrations in the calculator to see the exact weights and how the true hydration changes.
Open the free calculatorFAQ
How do I calculate sourdough starter percentage?
Divide the starter weight by the flour weight and multiply by 100. For example, 100 g of starter with 500 g of flour is 20%.
How much starter should I use for 500 g of flour?
A common starting point is 20%, which is 100 g. Many recipes use anything from 50 g (10%) to 150 g (30%), depending on kitchen temperature and how long you want bulk fermentation to take.
Does the starter count toward dough hydration?
Yes, physically it does: the starter's water and flour end up in the dough. With 100 g of 100% hydration starter, you add 50 g of flour and 50 g of water. The calculator shows true hydration with this included.
Can I use more starter to speed things up?
Generally, yes. More starter usually shortens bulk fermentation, and less starter lengthens it. Temperature has a similarly large effect.