How to build the right amount of levain — every time
A levain (or "starter build") is the off-shoot of your mother starter that you mix specifically for a bake. Build too little and you're short for your orders; build too much and you waste flour. The fix is to work backward from the levain your recipe calls for, using your feeding ratio.
Reading a feeding ratio (1:5:5)
A feeding ratio is ripe starter : flour : water by weight. 1:5:5 means: 1 part of your existing ripe starter, 5 parts flour, 5 parts water. Those parts add up to 11. To make a target amount of levain T, each component is just its share of the parts:
parts = S + F + W
ripe starter = T × S ÷ parts
flour = T × F ÷ parts · water = T × W ÷ parts
So 200 g of levain at 1:5:5 is about 18 g ripe starter, 91 g flour, and 91 g water. Add a 10–20% buffer for what clings to the jar and spoon.
How inoculation and temperature change the timing
The inoculation — how much ripe starter you use relative to the fresh flour — sets the pace. A small inoculation (1:5:5 ≈ 20%) ferments slowly and suits an overnight build; a big one (1:1:1 = 100%) ripens in a few hours. Temperature then scales that: every ~8°C (about 15°F) warmer roughly halves the time, and cooler roughly doubles it. This calculator combines both into a ready-in estimate — but always trust your eyes: use the levain when it has roughly doubled, looks domed and bubbly, and floats in water.
Stiff vs. liquid levain
Feed with less water than flour (say 1:5:3) and you get a stiff levain — it ferments more slowly, holds longer at its peak, and gives a milder, less sour crumb. Equal flour and water (1:5:5) is a classic liquid levain. The calculator shows the resulting hydration so you know what you're building.
Keep going: Baker's Percentage Calculator · How to scale a sourdough recipe · Try the free DoughPlan planner