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Sourdough starter
Also called sourdough discard, sourdough culture, wild yeast starter, levain, wheat sourdough starter, sourdough
172–240g6.1–8.5 oz
Sources disagree by 39%, more than the 5% tolerance, so the range is the answer.
What each source weighs for 1 cup
5 sources · 40% apart- Living Bread Baker172 g
- Peter Reinhart198 g
- Jeffrey Hamelman226 g
- King Arthur234 g
- Sourdoughstarter.com converter240 g
King Arthur Baking, 234 g: inside the range the sources span.
Sourdough starter in grams, by amount
- 1 cup172–240 g6.1–8.5 oz
- ¾ cup129–180 g4.6–6.3 oz
- ⅔ cup114.7–160 g4–5.6 oz
- ½ cup86–120 g3–4.2 oz
- ⅓ cup57.3–80 g2–2.8 oz
- ¼ cup43–60 g1.5–2.1 oz
- 1 tbsp10.8–15 g0.38–0.53 oz
- 1 tsp3.6–5 g0.13–0.18 oz
Weights for a US cup of 236.6 ml and spoons derived from it. Ounces are weight ounces of 28.35 g.
One US cup of sourdough starter weighs between 172 and 240 grams (6.1 to 8.5 ounces), depending on the brand or product and which source measured it. That range is the answer; a single number would not be. Every figure behind it is below, with the method each source used.
Most sites print one number for a cup of sourdough starter. This page prints 172 to 240 grams, because that is what King Arthur Baking Company – Ingredient Weight Chart, Jeffrey Hamelman – Bread: A Baker's Book of Techniques and Recipes, Living Bread Baker – active vs. discard density study, Peter Reinhart – The Bread Baker's Apprentice (88% hydration seed starter) and Sourdoughstarter.com converter – hydration breakdown actually measured, and it names the method behind every figure rather than picking a favourite.
Two or more sources measured this kind of product and still disagree, by 39.5%. That is more than this site will average over, so all the figures stand and none is chosen. Sourdough starter density spans 172-280 g/cup, a 63% spread driven by three independent physical variables: hydration ratio (65% stiff vs 100% standard vs 125% liquid), activity state (freshly-fed active vs peak-and-deflated), and flour type (white vs whole grain). King Arthur's chart range of 227-241 g/cup covers only one configuration: standard 100% hydration mid-cycle wheat starter. Recipes rarely specify which configuration they assume, and no single value defensibly represents all sourdough starter measurements.
| Filling the cup | 1 cup | Source |
|---|---|---|
| Standard, 100% hydration | 234 g8.3 oz | King Arthur Baking Company – Ingredient Weight Chart |
| Standard, 100% hydration | 226 g8 oz | Jeffrey Hamelman – Bread: A Baker's Book of Techniques and Recipes |
| Standard, 100% hydration | 172 g6.1 oz | Living Bread Baker – active vs. discard density study |
| Standard, 100% hydration | 198 g7 oz | Peter Reinhart – The Bread Baker's Apprentice (88% hydration seed starter) |
| Standard, 100% hydration | 240 g8.5 oz | Sourdoughstarter.com converter – hydration breakdown |
Sourdough starter ounces to grams and cups
| Weight | Grams | US cups |
|---|---|---|
| 1 oz | 28.3 g | 0.12–0.16 |
| 4 oz | 113.4 g | 0.47–0.66 |
| 8 oz | 226.8 g | 0.95–1.32 |
| 16 oz (1 lb) | 453.6 g | 1.89–2.64 |
Why this page publishes a range
Sourdough starter weighs 172-280 g/cup depending on three independent variables. King Arthur's chart lists 227-241 g/cup, which covers standard 100% hydration wheat starter mid-feeding-cycle, but a freshly-fed active starter can be as light as 172 g/cup and a stiff or deflated discard can reach 280 g/cup.
Sourdough starter is a fermented paste of flour and water, colonized by wild yeasts and lactic acid bacteria. The three physical variables that determine density:
**1. Hydration ratio.** Hydration is the weight of water divided by the weight of flour, expressed as a percentage. A 100% hydration starter has equal parts flour and water by weight and forms a pourable batter. A stiff 65% hydration starter has proportionally more flour and forms a putty-like paste. A liquid 125% hydration starter is thin enough to pour like heavy cream. Stiffer starters weigh more per cup (roughly 260 g at 65%) because they contain proportionally more dense flour per unit water. Liquid starters weigh slightly less (roughly 215 g at 125%) because water alone at 237 g/cup is less dense than the flour-water paste.
**2. Activity state.** A freshly-fed starter at peak activity contains substantial trapped CO2 from yeast metabolism, and that gas inflates the volume without adding mass. A freshly-peaked 100% hydration starter can measure as low as 172 g/cup while chemically identical starter after collapsing (discard) can reach 280 g/cup — a 63% swing in the same starter at different times of day. Where you are in the feeding cycle matters more than most recipes acknowledge.
**3. Flour type.** Starters maintained on white flour, whole wheat, rye, or blended flours have different base densities. Whole wheat and rye starters are noticeably heavier per cup than white starters at the same hydration and activity, because the flour itself is denser.
King Arthur's chart entry at 227-241 g/cup is one of only a handful of range-published entries on their weight chart, and it covers the most common configuration: standard 100% hydration wheat starter measured a few hours after feeding when it is active but not at its aeration peak. This is the mental model most recipe developers assume when they write '1 cup of starter' without further specification. The KA range is honest and does not need correction.
Interpreting recipes that call for '1 cup of sourdough starter': the recipe developer almost certainly means 100% hydration wheat starter, mid-cycle, in the 220-240 g range. If your starter is at that configuration, measure by cup or weigh at 230 g. If your starter is stiffer, more liquid, freshly-peaked, or made with different flour, weigh instead and target 230 g total, adjusting the recipe's water and flour to compensate for the difference in your starter's flour-to-water ratio.
**Discard vs. active starter.** Discard is not chemically different from active starter — it is the same culture, just unfed and past its activity peak. Discard weighs more per cup (roughly 250-280 g) because the CO2 has escaped and the paste has settled. Recipes that specifically call for discard usually expect 240-250 g/cup and have been tested with older, denser starter. Substituting active starter for discard by cup measurement will give roughly 20% less mass of ingredient than the recipe expects, which affects bulk fermentation timing and final texture.
**Levain.** Some professional recipes use 'levain' to mean a purpose-built starter portion, often at a different hydration than the maintained mother starter. When a recipe calls for levain by weight, follow the weight. When it calls for levain by cup, treat it the same as generic 100% hydration active starter unless the recipe specifies otherwise.
Practical guidance: weigh sourdough starter. This is the ingredient in serious baking where volume measurement is least reliable, and where a 5-10% error compounds significantly across bulk fermentation, dough hydration, and final crumb. For volume-only recipes, 227 g/cup is the safest single-number assumption, and matches KA's lower bound. For any precision work, weigh.
Sources
Standard, 100% hydration — no single figure published
Sourdough starter density spans 172-280 g/cup, a 63% spread driven by three independent physical variables: hydration ratio (65% stiff vs 100% standard vs 125% liquid), activity state (freshly-fed active vs peak-and-deflated), and flour type (white vs whole grain). King Arthur's chart range of 227-241 g/cup covers only one configuration: standard 100% hydration mid-cycle wheat starter. Recipes rarely specify which configuration they assume, and no single value defensibly represents all sourdough starter measurements.
- King Arthur Baking Company – Ingredient Weight Chart234 g per cup8.3 oz1 cup = 8 to 8.5 oz = 227-241 g. KA publishes as a range, one of only a handful of range-published entries on their chart. The KA range assumes standard 100% hydration wheat starter mid-cycle (fed but not yet peaked). No correction needed — KA's figure is consistent with Jeffrey Hamelman's professional reference and sits centrally within the physical range for this configuration.
- Jeffrey Hamelman – Bread: A Baker's Book of Techniques and Recipes226 g per cup8 oz'Two tablespoons of liquid (100% hydration) weighs 1 ounce' — 16 tablespoons per cup, so 8 ounces = 226 g/cup. Hamelman is a leading professional baking reference (former head baker at King Arthur), and his figure for 100% hydration starter matches the low end of the KA chart range exactly. This is the standard 100% hydration reference figure.
- Living Bread Baker – active vs. discard density study172 g per cup6.1 ozOne cup of active 100% hydration starter weighs approximately 172 g; one cup of discard (deflated, unfed for hours or days) weighs approximately 280 g. The 63% swing between active and discard reflects trapped CO2 in the active starter that inflates volume without adding mass. Same starter, same hydration, same flour — completely different density depending on where in the feeding cycle it sits when measured.
- Peter Reinhart – The Bread Baker's Apprentice (88% hydration seed starter)198 g per cup7 oz1 cup of Reinhart's seed starter at 88% hydration = 7 oz = 198 g/cup. Lower hydration (more flour, less water proportionally) produces a denser paste — but Reinhart's figure sits lower than expected for a stiffer starter, likely because his seed starter was still quite active. Illustrates that hydration alone doesn't determine density without also knowing activity state.
- Sourdoughstarter.com converter – hydration breakdown240 g per cup8.5 oz100% hydration active starter: 240 g/cup. Stiff 65% hydration: 260 g/cup. Higher hydration (125%): approximately 215 g/cup. Documents the hydration-dependent density spread independently of activity state — stiffer starters weigh more per cup because they contain proportionally more flour per unit water and trap less air.
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