Molecular biology
How do you calculate pCR master mix?
Scale a per-reaction recipe to a batch, with overage. The relationship used is mix = per-reaction x samples x (1 + overage).
Worked example
Every number below is computed by the calculator, not typed in
What you are given
- Components (per reaction): [{"name":"2x master mix","perReactionUl":"10"},{"name":"Forward primer (10 µM)","perReactionUl":"1"},{"name":"Reverse primer (10 µM)","perReactionUl":"1"},{"name":"Template","perReactionUl":"2"}]
- Reaction volume (µL): 20
- Number of samples: 24
- Overage %: 10
Formula: mix = per-reaction x samples x (1 + overage)
The working
- Effective reactions:
samples · (1 + overagePct / 100) = 24 · (1 + 10 / 100) = 26.4 - Water per reaction:
reactionVolumeUl - sum(components) = 20 - 14 = 6 µL - Total mix:
reactionVolumeUl · effectiveReactions = 20 · 26.4 = 528 µL
Master mix for 26.4 reactions (24 samples plus overage), total 528 µL.
Open this example in the calculator
What each symbol means
- neff: Effective reactions (samples plus overage)
- nₛₐₘₚ: Number of samples
- p: Overage percentage (%)
A printable one-page version is on the formula sheet.
Do it with your own numbers.
The PCR master mix calculator is free, shows every step, flags the hazards, and works offline once loaded. No account, no signup.
Open the calculator