This serial dilution calculator plans a stepwise dilution series: the concentration at every tube, the transfer and diluent volumes, and the total dilution the series reaches.
| Tube | Concentration | Transfer in | Diluent |
|---|
Recipe per tube: transfer = final volume ÷ factor (e.g. 0.1 mL into 0.9 mL diluent for 1:10 at 1 mL). Errors compound multiplicatively down a series — sloppy early pipetting poisons every later tube, which is why serial protocols worship mixing and fresh tips. Single-step dilutions live on the Dilution Calculator.
Each Tube Divides Again — Logarithms You Can Pipette
Serial dilution turns multiplication into repetition: the same transfer, n times, spans orders of magnitude no single dilution reaches precisely. Standards for calibration curves, MIC assays, and viral titers all live here — single jumps belong to our Dilution Calculator (C₁V₁ = C₂V₂). Part of our Biology Calculators collection.
Worked Example (Verified)
- 1 M stock, 1:10 × 6 tubes, 1 mL each (defaults): concentrations 10⁻¹, 10⁻², 10⁻³, 10⁻⁴, 10⁻⁵, 10⁻⁶ M; every tube = 0.1 mL transfer + 0.9 mL diluent; total dilution 1,000,000×
- Half-log series: factor √10 ≈ 3.16 gives finer ladders (1, 0.316, 0.1, 0.0316…) — dose-response curves’ preferred spacing; set factor 3.16 here
- Two-fold series: factor 2 across 8 tubes spans 256× — antibody titers speak in these (1:2 → 1:512 endpoints)
- The last-tube problem: tube 6 in the defaults holds 1 µM — signals there are 1 pipetting error from fiction; replicate and average
Technique Notes
- Change tips every transfer — carryover of even 1% wrecks high-factor series.
- Mix each tube thoroughly before transferring; concentration gradients are silent series-killers.
- Plate/spread promptly from dilutions: cells keep growing (or dying) in the tube, drifting the nominal factor.
- Volume accuracy dominates at small finals: 0.1 mL transfers deserve a calibrated micropipette, not a graduated cylinder’s optimism.
Related Tools
- Dilution Calculator — single-step C₁V₁ = C₂V₂
- CFU Calculator — where dilution series end up counted
- Biology Calculators — the full collection
Frequently Asked Questions
How do you calculate a serial dilution?
Each step divides the previous concentration by the step factor: Cₙ = C₀ ÷ fⁿ. A 1 M stock through six 1:10 steps ends at 10⁻⁶ M. Transfers are final-volume ÷ factor (0.1 mL into 0.9 mL diluent makes 1 mL of a 1:10 step). This calculator tabulates every tube.
What does “1:10 dilution” mean exactly?
One part sample in ten parts total: 1 part + 9 parts diluent (the common bench convention used here). Some fields write 1:10 as 1+10 (one in eleven) — check your protocol’s convention; the difference is 10% and compounds down the series.
Why use serial instead of one big dilution?
Precision: pipetting 0.1 µL for a single 10⁶× jump is impossible; six repeatable 0.1 mL transfers are routine. Serial steps also create the intermediate concentrations calibration curves and titer endpoints actually need. The tradeoff is error compounding — each step’s small inaccuracy multiplies forward.
How many dilution steps do I need?
n = log(total dilution) ÷ log(step factor): reaching 10⁻⁶ from stock with 1:10 steps needs 6; with 1:2 steps, ~20. Shallower factors give denser ladders near the action (dose-response), steep factors span range faster (plating for CFU counts).
What’s a half-log dilution series?
Steps of √10 ≈ 3.16×, halving the exponent each tube (10⁰, 10⁻⁰·⁵, 10⁻¹…): twice the resolution of a log series at the same tube count, with concentrations like 0.316 and 0.0316 that read oddly but curve-fit beautifully.
Is this serial dilution calculator free?
Yes — free, instant, no sign-up.