Recipe scaler
Scale a recipe to a different batch size and keep every concentration the same.
The batch the numbers below belong to.
Scaling works downwards too.
Components
For 25 mL · ×2.5
Supplement
2.3% of the batch
Medium, to make up
Bringing the batch to volume
Your stock must be 10.87 mg/mL for that to come out right. Unchanged by the scaling.
amount_new = amount_old × (batch_new ÷ batch_old)- Amount concentration, the ratio scaling preserves — IUPAC Compendium of Chemical Terminology (the Gold Book), 2019
Every concentration is preserved because both the component and the batch scale by the same factor. This assumes the components add to the volume — if your recipe means “make up to” rather than “add to”, the medium figure above is the one to use.
When to use this
Use this when a recipe is written for one batch size and you need a different one, and every concentration must stay the same. It is the unitary method applied to a whole recipe. If you need to reach a target concentration from a stock of known strength, use the dilution calculator instead.
Worked example
A protocol adds 230 µL of a supplement to make up 10 mL of medium. You want 25 mL.
- Recipe is written for
- 10 mL
- You want to make
- 25 mL
- Supplement
- 230 µL
Result
Made up to 25 mL with medium — 24.43 mL of it. The factor is 2.5 throughout.
What people get wrong
- Scaling some components and not others. Every component takes the same factor, including the ones that felt like round numbers at the original scale.
- Forgetting that the medium is what makes up the difference, not an extra 25 mL on top of the components.
- Scaling down past what a pipette can deliver. A component that becomes 0.5 µL needs an intermediate dilution, not a steadier hand.
Questions
+Do I need to know the concentration of the supplement?
No. The concentration cancels — what is preserved is the ratio of component to batch. Supplying it only lets the tool report what the stock must be, which is a useful check on an inherited recipe.
+Can I scale a recipe with powders in it?
Yes. Masses scale by the same factor but do not displace medium, so the make-up volume stays correct.
+Does this work for a PCR master mix?
Yes — treat one reaction as the reference batch and the number of reactions as the target, remembering to add overage for pipetting loss.
Related tools
- Dilution calculator — Work out how much stock and diluent to combine for a target concentration.
- Molarity calculator — Convert between mass, molar concentration and volume for a solution.
- Serial dilution calculator — Plan a dilution series and get the transfer volume for every step.
Science last reviewed .