Sourdough Starter Feeding Calculator
Why Exact Measurements Make or Break Your Starter
TL;DR: Eyeballing sourdough starter feedings is the number-one reason starters fail. Too much flour dilutes the culture. Too little water throws off hydration and slows fermentation. This calculator gives you exact gram measurements every time so you never have to guess.
Lemme tell you something I learned the hard way. I spent two weeks feeding my first starter "about a spoonful" of flour and "a splash" of water. And every single day it sat there, flat and confused, like it was waiting on me to make a decision.
Turns out? It was.
What Is a Feeding Ratio?
A feeding ratio describes how much starter you keep relative to the flour and water you add. The 1:1:1 ratio means equal parts of each — if you keep 50g of starter, you add 50g flour and 50g water. Simple. Consistent. Predictable.
The 1:5:5 ratio keeps 50g but adds 250g flour and 250g water. More food = slower fermentation = longer rise time. Great for overnight baking or if your kitchen runs warm and your starter burns through food too fast.
| Ratio | Best For | Rise Time at 77°F |
|---|---|---|
| 1:1:1 | Daily maintenance | 4–6 hours |
| 1:2:2 | Less frequent feeding | 6–10 hours |
| 1:5:5 | Overnight / hot kitchens | 10–16 hours |
What Hydration Should You Use?
100% hydration is equal weights flour and water. It's the standard for most home bakers — pourable like thick pancake batter, easy to stir, easy to judge. Most recipes that call for "sourdough starter" are written assuming 100% hydration.
75% and 50% hydration produce stiffer starters. Stiff starters ferment more slowly, produce less acetic acid (less sour), and are used in Italian-style baking. Unless a recipe specifically calls for a stiff starter, stick with 100%.
How to Read the Results
The calculator shows four numbers: how much starter to keep (discard the rest), how much flour to add, how much water to add, and your total jar weight after feeding. Write down that last number on a rubber band stretched around the jar. When your starter doubles — when it hits twice that number — it's at peak rise and ready to bake with.
Need the full picture? Our sourdough starter feeding guide covers timing, ratios, what to do when things go wrong, and how to read your starter's behavior across different seasons. And if you're just starting out, our beginner's guide walks you through the whole build process day by day.
Don't have a starter yet? The Mother is a 288-year-old live culture — free with the cost of postage. Feed it twice and you're baking within 48 hours. She responds very well to consistent, measured feedings.