Serial Dilution Calculator
Enter a starting concentration and a per-step dilution factor to build the whole series, or work backward from a target concentration.
Worked examples
Three-step 1:10 serial dilution
A calibration curve needs concentrations spanning three orders of magnitude from a 1 M stock, stepped down 1:10 at a time.
- C₀
- 1 M
- 1 : N
- 10
- Steps
- 3
Final 0.001 M — total dilution 1,000×
Five-step antibody titration
A lab titrates an 800 µg/mL antibody stock through five 1:2 steps to find the working dilution for an assay.
- C₀
- 800 µg/mL
- 1 : N
- 2
- Steps
- 5
Final 25 µg/mL — total dilution 32×
How the formula works
Each step of a serial dilution is an ordinary C₁V₁ = C₂V₂ dilution applied to the tube in front of it, using the same dilution factor N every time — so the concentration is divided by N once per step, not once total. After n steps that's N multiplied by itself n times, giving a total dilution of Nn. Working backward, if you know your starting and target concentrations, the number of steps needed is the base-N logarithm of how many total fold-changes you need.
Frequently asked questions
What's the difference between a serial dilution and a single dilution?
A single dilution (C₁V₁ = C₂V₂) gets you from a stock to a target concentration in one step. A serial dilution repeats the same 1:N dilution step several times in a row, using each tube's output as the next tube's stock — it's the standard way to reach very large fold-changes (1,000×, 100,000×) without needing to measure an unrealistically tiny volume of the original stock.
Why is a serial dilution more accurate than one big dilution for large fold-changes?
Pipettes are most accurate in their mid-range — typically tens of microliters to a few milliliters. A single 1:10,000 dilution might require measuring 0.1 µL of stock, where small errors become huge relative errors. Splitting that into four 1:10 steps keeps every transfer inside a normal, accurately-pipettable volume range, so the error at each step stays small and doesn't compound into a large one.
What does a '1:N dilution factor' mean?
It means 1 part of solution combined with enough diluent to make N total parts — so a 1:10 dilution is 1 part solution plus 9 parts diluent, and it divides the concentration by 10. It's the same dilution factor applied identically at every step of the series.
Why does the total dilution multiply instead of add across steps?
Each step divides the concentration by N again, and dividing repeatedly is multiplication, not addition — three 1:10 steps give 10 × 10 × 10 = 1,000-fold total, not 10 + 10 + 10 = 30-fold. This is why a small number of steps reaches an enormous total dilution very quickly.
What's the difference between the transfer volume and the diluent volume at each step?
The transfer volume is what you carry over from the previous tube (already-diluted solution); the diluent volume is the fresh solvent you add to it in the new tube. Because the dilution factor and the diluent volume per step are both constant, the transfer volume and the total volume in every tube also work out to be the same at each step — this calculator shows all three when you turn on the volumes option.
How do I minimize error across a long dilution series?
Use a fresh pipette tip for every transfer so you never carry concentrated solution forward by accident, mix each tube thoroughly (vortex or pipette up-and-down) before drawing from it for the next step, and keep your transfer volume inside your pipette's accurate range — if the calculated transfer volume is too small to pipette reliably, increase the diluent volume per step so the transfer volume scales up with it.