Serial Dilution Calculator
Plan a complete dilution series in seconds. Enter the stock concentration, the dilution factor (or the final concentration you need), the number of tubes and the volume per tube to get the concentration in every tube, how much to transfer and how much diluent to add.
Last updated:
10 = 1:10 (ten-fold), 2 = 1:2 (two-fold)
Concentration wanted in the last tube
How to use the Serial Dilution Calculator
- Enter the stock concentration and pick its unit.
- Choose a dilution factor per step (10 for ten-fold, 2 for two-fold) or switch to a target final concentration.
- Set the number of tubes and the final volume you want in each.
- Read the transfer and diluent volumes and the concentration of every tube in the table.
- Download the table as CSV to print or paste into your lab notebook.
Serial dilution formulas
| Quantity | Formula | Example (1 mg/mL, DF 10, 1 mL) |
|---|---|---|
| Concentration in tube k | C_k = C₀ ÷ DF^k | Tube 3: 1 ÷ 10³ = 0.001 mg/mL |
| Total dilution after k steps | DF^k | 1:1,000 after 3 steps |
| Transfer volume | V_t = V_f ÷ DF | 1 mL ÷ 10 = 0.1 mL |
| Diluent volume | V_d = V_f − V_t | 1 − 0.1 = 0.9 mL |
| Factor for a target | DF = (C₀ ÷ C_n)^(1/n) | (1 ÷ 0.001)^(1/3) = 10 |
This tool plans a whole series of equal steps. For a single dilution with C₁V₁ = C₂V₂ use the Dilution Calculator.
Common dilution series
| Series | Transfer + diluent (1 mL final) | Total after 4 steps | Typical use |
|---|---|---|---|
| Two-fold (1:2) | 500 µL + 500 µL | 1:16 | MIC tests, titrations, ELISA standards |
| Three-fold (1:3) | 333.3 µL + 666.7 µL | 1:81 | Dose-response curves |
| Five-fold (1:5) | 200 µL + 800 µL | 1:625 | Antibody titrations |
| Ten-fold (1:10) | 100 µL + 900 µL | 1:10,000 | Plate counts (CFU), qPCR standard curves |
| Hundred-fold (1:100) | 10 µL + 990 µL | 1:100,000,000 | Very concentrated cultures |
Tips: mix every tube well before taking the next aliquot, change tips between transfers to avoid carry-over, and avoid transfers below about 1–2 µL, where pipetting error grows quickly.
Frequently asked questions
What is a serial dilution?
A serial dilution is a stepwise series of dilutions where each tube is made from the previous one using the same dilution factor. A ten-fold series from 1 mg/mL gives 0.1, 0.01, 0.001 mg/mL and so on, which lets you reach very low concentrations accurately.
How do you calculate the concentration after a serial dilution?
Divide the stock concentration by the dilution factor raised to the number of steps: C_n = C₀ ÷ DF^n. Six ten-fold steps from 1 mg/mL give 1 ÷ 10⁶ = 0.000001 mg/mL (1 ng/mL).
How much do I transfer in each step?
Transfer volume = final volume ÷ dilution factor, and diluent = final volume − transfer. For a 1:10 dilution with 1 mL final volume, move 100 µL into 900 µL of diluent.
What is the difference between 1:10 and 1 in 10?
In most lab usage both mean one part sample in ten parts total (1 part sample + 9 parts diluent), a dilution factor of 10. Some fields write 1:9 for one part sample to nine parts diluent; this calculator always uses the total-volume convention (DF = total ÷ sample).
Why does the first tube lose volume?
Each tube gives part of its volume to the next tube, so all tubes except the last end up with less than the final volume. Tick 'Keep the full final volume' to have the calculator prepare extra in each tube so every tube keeps the full volume after transferring.
How do I find the dilution factor for a target concentration?
Use DF = (C₀ ÷ C_target)^(1/n). To go from 1 mM to 1 µM (1000×) in 3 equal steps, DF = 1000^(1/3) = 10 per step.
How is a serial dilution used to count bacteria?
A culture is diluted ten-fold several times and a known volume of a high dilution is plated. Colonies are counted on a plate with a countable number (often 30–300), and CFU/mL = colonies ÷ (volume plated in mL × total dilution).
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.