Your result
Click Calculate
Enter your values, then click Calculate result.How this calculator helps
This sourdough starter calculator converts a starter:flour:water feeding ratio into weighed ingredients and final hydration. Choose whether to start from the seed you will retain or from a desired total starter mass. Enter the seed’s existing hydration because retained starter already contains both flour and water. The result keeps seed mass, added flour, added water and final total separate, then computes hydration from the entire mixture. It is a feeding and levain-build arithmetic tool, not a fermentation timer. Ratios, temperature, flour and starter condition affect the real process, but this page does not invent a precise peak time or certify that a culture is safe or ready for bread.
How to use it
- 1
Choose retained-seed mode or desired-final-total mode.
- 2
Enter the relevant mass in grams and the starter, flour and water ratio parts.
- 3
Enter the existing seed hydration as water mass divided by flour mass.
- 4
Click Calculate result to inspect seed, fresh ingredients, total and final hydration.
- 5
Weigh ingredients with a suitable scale and assess the actual starter independently.
Formula and methodology
For ratio parts S:F:W and retained seed mass m, added flour = mF/S and added water = mW/S. Total = m(1 + F/S + W/S). In final-total mode, seed m = desired total/(1 + F/S + W/S). At existing hydration h%, seed flour = m/(1 + h/100), seed water = m − seed flour. Final hydration = 100 × (seed water + fresh water)/(seed flour + fresh flour).
The calculator applies the displayed arithmetic to the values entered on this device. It does not silently load a local tax rate, currency conversion or commercial assumption.
Worked calculation example
Retaining 50 g of a 100% hydration seed and using 1:2:2 adds 100 g flour and 100 g water, giving 250 g total. The seed contains 25 g flour and 25 g water, so the combined mixture has 125 g of each and remains at 100% hydration. With a 50% hydration seed, the same feed contains about 33.333 g seed flour and 16.667 g seed water; final hydration becomes 116.667/133.333 × 100 = 87.5%. To build 250 g total at the same 1:2:2 ratio, reverse mode returns 50 g seed rather than assuming that the target itself is retained starter.
How to interpret your result
The total is the mathematical mass after feeding, before real handling losses or evaporation. Fresh ingredient results do not include the flour and water already in the seed; final hydration does. A positive starter ratio and fresh flour ratio are required. Fresh water may be zero for a deliberately modeled stiff mixture, but that mathematical allowance is not a recommended culture-maintenance method.
For different inputs or formulas, use Ratio Calculator; Grams / Millilitres Calculator; Cake Pricing Calculator.
Related questions this calculator covers
- sourdough starter calculator
- sourdough feeding ratio calculator
- starter hydration calculator
- levain build calculator
- 1:2:2 starter ratio
Scenario comparison
| Scenario | What it shows |
|---|---|
| Known seed | fifty grams at 1:2:2 builds two hundred fifty grams. |
| Reverse build | a two hundred fifty gram target returns the same seed and additions. |
| Stiff seed | a fifty-percent seed changes final hydration despite equal fresh additions. |
Common mistakes to avoid
- Treating starter:flour:water parts as volume measures.
- Ignoring flour and water already in the retained seed.
- Entering desired final mass as though it were the seed amount.
Add seed, fresh flour and fresh water to check total mass. Divide final water by final flour to check hydration. Feed the calculated total back through the opposite direction with unchanged ratios and seed hydration; it should recover the original seed. Round only as required by the scale, then recompute what the rounded actual weights imply.
Authoritative reference. Sources support the stated context. Worked examples, scenario boundaries and verification arithmetic are independently authored by SolvePilot; no affiliation is claimed.Keep recipe starter separate from maintenance starter
A recipe may require a particular levain amount while you also want to retain some culture for later use. The final-total field represents only the build being calculated. If you want an extra reserve, include it explicitly in that target or calculate a separate maintenance feed. Do not assume that the tool has already set aside a universal starter reserve.
For a recipe requiring 200 g plus a deliberately chosen 50 g reserve, a 250 g target at 1:2:2 produces 50 g seed and 100 g of each addition. That comparison organizes quantities but does not establish that a fifty-gram reserve is suitable for every routine. Record the requirement and chosen reserve separately so another baker can see why the target is larger than the recipe quantity.
Compare ratio changes while holding the seed constant
With fifty grams retained, 1:1:1 yields 150 g total and 1:3:3 yields 350 g. Both remain at one hundred percent hydration if the seed is at that hydration. The larger total results from extra fresh ingredients, not extra seed. This makes a ratio comparison useful for planning flour use and available jar capacity.
Changing only water parts changes hydration as well as mass. Keep the two outputs distinct: a larger quantity is not automatically a wetter mixture, and a higher hydration is not a claim of better flavor or healthier culture. The worksheet shows the actual water-to-flour relationship so the recipe assumptions stay visible.
Round ingredients deliberately on a kitchen scale
Decimal outputs show the unrounded arithmetic. A kitchen scale may not resolve every displayed fraction of a gram. Choose a practical weighing precision, write down the actual masses and check the resulting total. Tiny display precision should never be mistaken for precise knowledge of the seed’s composition.
Use reverse mode as a quick independent check before weighing. If the final mass returns the original retained seed under unchanged settings, the direction and ratios are consistent. Inputs remain drafts until Calculate is clicked; the earlier submitted build stays visible during edits, making it easier to compare a maintenance feed with a recipe build without losing the original figures.
What can affect the result?
Weight convention
Feeding ratio parts are masses. Equal cups of flour and water are not equal masses. The worksheet deliberately uses grams rather than inventing flour density from a cup measurement. Use the same mass unit when checking a recipe outside the tool.
Seed composition
The retained seed is not pure flour and is not pure water. Omitting its composition can give the wrong final hydration, especially for a stiff starter or a small feed. Existing hydration is required in both calculation directions.
Final-total direction
A desired levain amount includes seed and all additions. Reverse mode divides by the combined ratio factor. It does not subtract an arbitrary seed allowance or assume every recipe uses the same inoculation proportion.
Fermentation conditions
A calculated feed quantity does not predict readiness at an exact hour. Temperature, flour, culture activity and handling can change development. Observe the actual starter and follow a reliable baking process rather than treating ratio arithmetic as a timer.
Privacy and browser processing
Values entered on this page are processed in the current browser session. SolvePilot does not require an account and does not receive the values entered into the calculator. Refreshing or closing the page clears the working values unless the browser itself restores a previous session. Avoid entering identifying or account information because the calculation needs summary values only.
Accuracy and verification
Accuracy depends first on input quality. Confirm definitions, scales, dates and source information before entering a value. Keep an independent record of any result used for planning because this page does not create an official statement or retain a calculation history.
Limits of this estimate
One-stage weighed feeding only. No peak-time prediction, multi-stage fermentation schedule, flour nutrition model, microbial-health assessment or food-safety guarantee. Starter hydration must be independently known. Results use floating-point arithmetic and sensible bounded inputs rather than claiming laboratory weighing precision.
Sources and review information
Frequently asked questions
What does a 1:2:2 feeding ratio mean?＋
One part retained starter, two parts fresh flour and two parts fresh water by weight. Fifty grams of seed therefore receives one hundred grams of each addition.
Does 1:2:2 always give 100% hydration?＋
Only when the retained seed composition is compatible. A stiff seed can leave the entire mixture below one hundred percent even with equal fresh additions.
How do I build an exact final starter amount?＋
Select desired-final-total mode and enter the total you want. The tool solves the seed and additions using the complete ratio factor.
Will the calculator tell me when it peaks?＋
No. It checks masses and hydration. Readiness depends on the actual culture and conditions, which are not inferred from the ratio.
Can I use cup measurements?＋
Convert to measured masses first. A cup of flour and a cup of water have different masses, and flour packing changes volume-based estimates.