Serial Dilution Calculator
Plan a serial dilution series. Enter the stock concentration and its units, the fold dilution per step (10 means a 1:10 step) and the number of steps to get the final concentration, the total dilution factor, and every step along the way.
Example: with Stock concentration 100 · Concentration unit µM · Fold dilution per step 10 · Number of steps 5 → Final concentration: 0.001 µM.
- Total dilution factor100,000-fold total (10x per step, 5 steps)
- Concentration at each step#1: 10, #2: 1, #3: 0.1, #4: 0.01, #5: 0.001 µM
Computed by the calculator below using its default values. Change any input to see your own numbers.
Each step multiplies the dilution: an n-step series diluted D-fold each time is a total dilution of Dⁿ. The final concentration is the stock divided by that total.
Why dilutions multiply
A serial dilution repeats the same small dilution several times, carrying a fixed volume forward at each step. Because each step multiplies the last, the dilutions compound: three 1:10 steps do not give 1:30, they give 1:1000. In general an n-step series with a D-fold dilution each time reaches a total dilution of Dⁿ, and the final concentration is the stock divided by that number.
Serial dilution is how labs reach very low, accurate concentrations. Pipetting a single 1:1,000,000 dilution directly would demand a microliter into a liter — impractical and imprecise. Six easy 1:10 steps get there with far less error, which is why the method is standard for cell counts, standard curves, and antibody titrations.
How it’s calculated
Total dilution = Dⁿ for n steps at a D-fold dilution each. Final concentration = C_stock / Dⁿ, and the concentration after step k is C_stock / Dᵏ, consistent with C1V1 = C2V2 applied step by step. Steps are capped at 20 and very small or large numbers are shown in scientific notation.
Every step uses the same dilution factor and mixing is complete. Pipetting error, adsorption to tubes, and volume loss are not modeled.
Ten-fold serial dilution of a 100 µM stock
| Steps (1:10 each) | Total dilution | Concentration |
|---|---|---|
| 1 | 1:10 | 10 µM |
| 2 | 1:100 | 1 µM |
| 3 | 1:1,000 | 0.1 µM (100 nM) |
| 4 | 1:10,000 | 0.01 µM (10 nM) |
| 5 | 1:100,000 | 0.001 µM (1 nM) |
| 6 | 1:1,000,000 | 0.1 nM |
Computed as C_stock / 10ⁿ; rounded.
Common mistakes
- Adding dilution factors instead of multiplying — three 1:10 steps is 1:1000, not 1:30.
- Confusing the fold dilution (10) with the dilution ratio (1:10); a 10-fold step is written 1:10.
- Forgetting to mix thoroughly before drawing the next transfer, which skews every later step.
- Carrying rounding errors down a long series instead of computing from the stock.
Frequently asked questions
How do you calculate a serial dilution?
Multiply the per-step dilution by itself once for each step: total dilution = Dⁿ. Divide the stock concentration by that total to get the final concentration.
What is the total dilution factor?
It is the fold dilution per step raised to the number of steps. Five 1:10 steps give 10⁵ = 100,000-fold total dilution.
What does a 1:10 dilution mean?
One part sample plus nine parts diluent, for ten parts total — a 10-fold dilution. Repeating it is what makes a serial dilution.
Why use a serial dilution instead of one big one?
Reaching extreme dilutions in a single step needs impractically tiny or huge volumes. Several moderate steps are more accurate and easier to pipette.