Serial Dilution
Calculator
Build multi-step dilution series with two-fold, ten-fold, or custom factors. Generate complete concentration tables for standard curves and assay plates.
What Is a Serial Dilution Calculator?
A serial dilution calculator computes the concentration at each step of a multi-step dilution series. You set a starting concentration, a dilution factor per step, and the number of tubes — the calculator generates a complete table showing every concentration in the series. Serial dilutions create logarithmically spaced concentrations used for standard curves, minimum inhibitory concentration (MIC) panels, and dose-response assays.
Benefits
- Generates complete concentration tables for any series
- Supports two-fold, five-fold, ten-fold, or custom factors
- Calculates transfer and diluent volumes per tube
- Shows total fold dilution from stock at each step
Applications
- Standard curve preparation for ELISA and qPCR
- MIC testing panels for antibiotic susceptibility
- Dose-response curves in pharmacology research
- Cell viability assays with serial drug dilutions
This serial dilution calculator handles any factor from 2 to 100 and generates up to 20 steps. Researchers performing qPCR standard curves with Bio-Rad CFX96 or Applied Biosystems QuantStudio instruments typically use 5-point or 7-point ten-fold serial dilutions. ELISA plate setup for cytokine quantification uses two-fold dilutions across 8 rows. The tool generates publication-ready concentration tables for both.
The Serial Dilution Equation
Every serial dilution follows one equation: Cₙ = C₀ ÷ DFⁿ, where C₀ is the starting concentration, DF is the dilution factor per step, and n is the step number. Each tube receives a fixed aliquot from the previous tube, gets diluted by the same factor, and passes an aliquot to the next.
Rearrange the equation to solve for any unknown:
V₁ = (C₂ × V₂) ÷ C₁— how much stock to pipetteC₂ = (C₁ × V₁) ÷ V₂— what concentration you'll getV₂ = (C₁ × V₁) ÷ C₂— total volume neededThis geometric progression creates logarithmically spaced concentrations — ideal for plotting log-linear standard curves. When the dilution factor is 10, each step reduces concentration by one order of magnitude: 1 M → 0.1 M → 0.01 M → 0.001 M. When the factor is 2, each step halves the concentration: 1 M → 0.5 M → 0.25 M → 0.125 M. The serial dilution formula applies identically whether you work with molar concentrations in a biochemistry lab or CFU/mL counts in microbiology.
Choosing the Right Serial Dilution Factor
The dilution factor determines the spacing between concentrations in your series. A two-fold serial dilution (DF = 2) provides fine resolution — useful for MIC testing where breakpoints fall at specific concentrations. A ten-fold serial dilution (DF = 10) covers a wider dynamic range — useful for qPCR standard curves that span 5–7 orders of magnitude.
The CLSI recommends two-fold serial dilutions for antimicrobial susceptibility testing. Bio-Rad, Promega, and New England Biolabs recommend ten-fold serial dilutions for qPCR efficiency calculations. Five-fold dilutions offer a middle ground for ELISA standard curves. This serial dilution factor calculator helps you select the factor that matches your assay's dynamic range requirements.
Step-by-Step Serial Dilution Calculator Guide
Follow these steps to calculate your dilution:
Practical Serial Dilution Protocols
Two-fold serial dilutions are the laboratory standard for antimicrobial MIC panels. Add equal volumes of bacterial broth to each well. Transfer half the volume from well 1 to well 2, mix, transfer half from well 2 to well 3, and continue. Discard the final transfer to maintain consistent volumes across all wells.
Automated liquid handlers from Hamilton, Beckman Coulter, and Tecan accelerate serial dilution in high-throughput screening. For manual dilution in 96-well plates, use multichannel pipettes with fresh tips at each transfer to prevent carryover. Labs performing ELISA standard curves with R&D Systems or BioLegend kits follow two-fold or three-fold serial dilution protocols specified in the product insert. This serial dilution calculator generates the complete concentration table and transfer volumes for any protocol.
Serial Dilution Calculator Example
Problem: A microbiologist needs a 7-step two-fold serial dilution of gentamicin starting at 128 µg/mL for MIC testing in a 96-well plate.
Cₙ = C₀ ÷ 2ⁿC₇ = 128 ÷ 2⁷ = 128 ÷ 128 = 1 µg/mLSeries: 128, 64, 32, 16, 8, 4, 2, 1 µg/mLTotal dilution = 2⁷ = 128× foldFrequently Asked Questions
Apply Cₙ = C₀ ÷ DFⁿ at each step. Choose a starting concentration (C₀), a dilution factor (DF), and the number of steps. At each step, transfer a fixed volume from the previous tube into fresh diluent. For a two-fold series: transfer half the volume and add an equal amount of diluent. For a ten-fold series: transfer one-tenth and add nine-tenths diluent. This serial dilution calculator builds the entire table automatically — enter your parameters and get a complete concentration series for standard curves, MIC panels, or dose-response experiments.
Two-fold halves the concentration at each step; ten-fold divides by 10. A two-fold series from 100: 100, 50, 25, 12.5, 6.25. A ten-fold series from 100: 100, 10, 1, 0.1, 0.01. Two-fold gives finer resolution (better for MIC breakpoints), while ten-fold covers more dynamic range per step (better for qPCR standard curves). Choose based on the assay sensitivity and the range of concentrations you need to test.
5 to 8 steps for most assays. qPCR standard curves typically use 5–7 points with ten-fold dilutions, spanning 5–7 orders of magnitude. ELISA standard curves use 7–8 points with two-fold dilutions. The number of steps depends on your assay dynamic range and the precision needed at each concentration. This serial dilution calculator lets you adjust the step count and factor until the concentration range matches your assay requirements.