What is a serial dilution?

A serial dilution is a series of successive dilutions where a fixed volume is transferred from one tube into the next. Each step multiplies the previous concentration by 1 / dilution factor, producing a geometric progression of concentrations.

What dilution factor should I use?

Common factors are 2 (1:2 dilutions, halving each step), 5, or 10. A factor of 10 is standard for bacterial counts; factor 2 is typical for antibody titrations. Choose based on the range of concentrations you need to cover.

How is concentration calculated at each step?

C_n = C_0 / (DF^n), where C_0 is the starting concentration, DF is the dilution factor, and n is the step number. For a 1:10 dilution starting at 1 mol/L: step 1 = 0.1, step 2 = 0.01, step 3 = 0.001 mol/L, and so on.

What is the transfer volume?

Transfer volume is the amount moved from one tube to the next. It equals the total tube volume divided by the dilution factor. For a 1:10 dilution in 1 mL total volume, you transfer 0.1 mL (100 µL) and add 0.9 mL of diluent.

Can I use this for non-molar units?

Yes. The math is the same regardless of unit — mol/L, mg/mL, µg/µL, CFU/mL, %, etc. Just pick the matching unit in the dropdown and the output labels update accordingly.

What is the difference between dilution factor and dilution ratio?

Dilution factor (DF) is the total fold-dilution: a 1:10 dilution has DF = 10. Dilution ratio is the fraction of sample in the mixture: 1/10. This calculator uses the dilution factor convention, which is the most common in lab protocols.

Serial Dilution Calculator

Enter your starting concentration, dilution factor, and number of steps to instantly calculate the concentration at every stage of a serial dilution.

Dilution Parameters

Starting Concentration

Dilution Factor

Each step is 1 part sample in 10 parts total.

Number of Steps

Volume per Tube (optional)

Total Vol.

Transfer Vol.

0.1 mL

Dilution Table

Set parameters on the left and click Calculate.

Step	Tube Label	Concentration	Cumulative Dilution	Transfer Vol.	Diluent Vol.

Done

Summary

A serial dilution is a stepwise reduction of a solution's concentration by repeatedly transferring a fixed volume into fresh solvent. This calculator computes the resulting concentration at each step so you can plan experiments without manual arithmetic. It supports any starting concentration, dilution factor, and unit.

How it works

Enter the starting (stock) concentration and select its unit (mol/L, mg/mL, %, etc.).
Set the dilution factor — for example 10 means each tube is 1 part sample in 10 parts total.
Choose how many dilution steps to perform (1–20).
Optionally set the total volume per tube and the transfer volume to see exact volumes.
Click Calculate to view a table of concentrations, dilution ratios, and transfer volumes for every step.
Copy the table or download results as CSV for your lab notebook.

Use cases

Preparing standard curves for ELISA or spectrophotometry assays.
Diluting bacterial cultures to countable densities for colony plating.
Creating a range of drug concentrations for dose-response experiments.
Verifying manual dilution calculations before running a PCR or qPCR assay.
Teaching dilution concepts in a classroom or lab training session.
Diluting reagents in food science, environmental testing, or quality control.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu