Reaction setup · Free Verbex lab tool

PCR and qPCR Master Mix Calculator

Enter your reactions and stocks. Verbex works out every volume per reaction and for the whole mix with excess, fills the rest with water, and checks that it all adds up.

Your numbersExample loaded
Components (water is calculated)
More optionsOptional
Notebook entryMath checked ✓
Make this much master mix910.8 µL
Dispense per well18 µL
Water per reaction6.4 µL

PCR master mix: IL-6 qPCR, plate 2

46 reactions + 10% excess (mix for 50.6 reactions). Dispense 18 µL of master mix per well. Then add 2 µL template to each well (20 µL per reaction).

ComponentStockFinalPer reactionMaster mix
2x SYBR Green master mix2×1×10 µL506 µL
Forward primer10 µM400 nM0.8 µL40.48 µL
Reverse primer10 µM400 nM0.8 µL40.48 µL
Nuclease-free water—to volume6.4 µL323.8 µL
Total mix18 µL910.8 µL

Formula: volume per reaction = final ÷ stock × reaction volume (or amount ÷ stock); water fills the rest

Check: components + water + template = 20 µL per reaction ✓; every final concentration recomputed from its volume ✓

Keep enzymes on ice and add them last; mix gently and spin down before dispensing.

Verbex Lab Tools · PCR master mix v1.0 · 2026-10-13 23:36 UTC · verify before use

How it is calculated

Every number shows its work.

Each component's volume per reaction is its final concentration divided by its stock concentration, times the reaction volume (C1 × V1 = C2 × V2). Enzymes and template can be given as an amount per reaction instead: volume = amount ÷ stock concentration.

Water fills whatever volume is left after the components and the template. If the components add up to more than the reaction volume, Verbex says so instead of returning a negative water volume.

The whole-mix volume is the per-reaction volume × reactions × (1 + excess). Pipetting tiny volumes into one big mix is far more accurate than adding 0.8 µL to every well.

Use it from your AI assistant

Add Verbex Lab Tools to Claude, ChatGPT or any MCP client and ask in plain words. Your agent calls the same calculation and gets this checked notebook entry back.

https://www.verbalexperiment.com/mcp

Tool name: pcr_master_mix. Free, no account, nothing stored.

Questions researchers ask

PCR Master Mix Calculator: common questions

How much excess should I make for a PCR master mix?

About 10% extra (or one to two extra reactions) covers the liquid lost on pipette tips and tube walls for most plates. Add more for viscous mixes or when dispensing many wells with a multichannel pipette.

How do I calculate the primer volume per reaction?

Divide the final concentration by the stock concentration and multiply by the reaction volume. For 400 nM final from a 10 µM stock in a 20 µL reaction: 0.4 µM ÷ 10 µM × 20 µL = 0.8 µL.

Should the template go into the master mix?

Usually not. Each well normally gets a different sample, so add the template to each well separately and make the master mix for the remaining volume. Put it in the mix only when every well gets the same template.

Why is water calculated last?

Water makes up the difference between the reaction volume and everything else, so it is the one volume you never choose directly. Calculating it last guarantees every reaction ends at exactly the right volume.

What if a component volume is below 0.5 µL?

Pipette it into the whole master mix, where the volume is much larger, rather than into each well. If even the whole-mix volume is tiny, make an intermediate dilution of the stock first. Verbex warns you when this happens.

More free lab tools

Plan the rest of the run.

96-Well Plate Map BuilderSerial Dilution Protocol PlannerMolarity and Solution Prep CalculatorAll Verbex lab tools
Verbex for iPhone and iPad

Running the plate?

Verbex records the run hands-free at the bench: speak deviations, time steps, and leave with the record done.

Try Verbex free