🧪 Dilution Series Generator – Complete Lab Protocol Tool
Whether you are setting up a dose-response curve, calibrating a standard curve, or preparing a serial antibody dilution, getting the volumes right at every step is critical. A single arithmetic error early in the sequence propagates through every subsequent tube, invalidating the whole experiment. This Dilution Series Generator eliminates bench-time arithmetic by computing the exact transfer volume and diluent volume at every step — and producing a ready-to-print lab protocol.
Four Dilution Modes
🔄 Serial (Uniform Factor)
Each tube is diluted from the previous one by the same factor. Ideal for creating a logarithmic concentration range quickly and efficiently with minimal stock solution.
⚗️ Custom Factors Per Step
Enter a different dilution factor at each step for non-uniform series — common in drug-response curves that require denser sampling around an expected EC₅₀.
🎯 Back-Calculation
Provide the stock concentration, desired final concentration, and dilution factor. The tool calculates the minimum number of steps required to reach your target.
📦 Direct (Parallel) Dilution
Each tube is prepared directly from the stock — not from the previous tube. Produces more accurate target concentrations for independent calibration standards.
The Core Formulas
Every dilution series is built on two equations that every chemist and biologist should know:
1. Concentration at Each Serial Step
Cₙ = C₀ / DFⁿ
Where:
Cₙ = concentration at step n
C₀ = stock (starting) concentration
DF = dilution factor (e.g. 10 for a 1-in-10 dilution)
n = step number (1, 2, 3 …)2. Transfer Volume – C₁V₁ = C₂V₂
V₁ = (C₂ × V₂) / C₁ → simplified to V₁ = V₂ / DF
Diluent volume = V₂ − V₁
Where:
C₁ = concentration of source (previous step)
V₁ = volume to transfer from source
C₂ = target concentration for this step
V₂ = desired total final volume for this step3. Back-Calculation – Steps Required
n = ⌈ log(C₀ / C_target) / log(DF) ⌉
The result is rounded up to ensure you reach or exceed the target.Worked Example – 1:10 Serial Dilution
Stock: 1000 µM | Dilution Factor: 10 | Steps: 6 | Volume per step: 1000 µL
| Step | Concentration | Transfer (µL) | Diluent (µL) | Cumulative Factor |
|---|---|---|---|---|
| Stock | 1000 µM | — | — | 1:1 |
| 1 | 100 µM | 100 | 900 | 1:10 |
| 2 | 10 µM | 100 | 900 | 1:100 |
| 3 | 1 µM | 100 | 900 | 1:1,000 |
| 4 | 0.1 µM | 100 | 900 | 1:10,000 |
| 5 | 0.01 µM | 100 | 900 | 1:100,000 |
| 6 | 0.001 µM | 100 | 900 | 1:1,000,000 |
Supported Concentration Units
The generator accepts concentrations in M, mM, µM, nM (molar units) and mg/mL, µg/mL, g/L, % w/v, % v/v (mass-based units). All conversions within a domain (molar ↔ molar, mass ↔ mass) are handled automatically. Volume units (µL, mL, L) are also interchangeable.
When to Use Each Mode
Choosing the right dilution strategy
Use serial dilution when you need many equi-spaced points on a log scale and want to conserve stock. Use direct dilution when accuracy of individual concentrations is paramount (e.g. calibration standards, regulatory work). Use back-calculation when you know your assay's target sensitivity range and need to find the optimal step count. Use custom factors for non-uniform drug-response series or when using a non-integer dilution scheme.
Tips for Accurate Dilutions
- Always mix thoroughly (vortex or pipette 5×) before taking the transfer volume for the next step.
- Use a fresh tip for each transfer to avoid carry-over contamination.
- For very large dilution factors (>100 per step), consider using two intermediate steps instead to reduce pipetting error.
- Pre-dispense the diluent volume into all tubes before starting transfers — this reduces the chance of step-order mistakes.
- When working with volatile solvents (e.g. DMSO), keep vials capped between steps to prevent evaporation-driven concentration changes.
- For µL-scale transfers (< 5 µL) pipetting precision drops significantly; consider scaling up your volumes or using a repeat-dispense pipette.
Export and Sharing
Once you have generated a protocol, use the Copy Table button to paste it directly into a lab notebook or ELN, or click Download CSV to import the protocol into Excel, GraphPad Prism, or your LIMS. Each export includes step number, concentration, transfer volume, diluent volume, cumulative fold-dilution, and any warnings about physically extreme values.