DNA and RNA dilution by mass concentration
A simple dilution conserves the amount of nucleic acid: stock concentration times stock volume equals target concentration times final volume. This page uses ng/µL and µL, so no unit conversion is needed when all fields follow those labels.
The equation assumes the stock is homogeneous and that volumes are additive. It does not correct concentration measurements for contaminants, degradation, or instrument bias.
How to calculate a nucleic acid dilution
- Confirm concentration basis: Use compatible mass concentrations for the same DNA or RNA preparation.
- Enter stock and target: Target concentration cannot exceed stock concentration by dilution alone.
- Enter final volume: Provide the total intended volume in µL.
- Check practical volumes: Verify both transfer volumes are within validated pipette ranges and protocol requirements.
Formula and variables
Solve V₁ = C₂V₂/C₁, then subtract stock volume from final volume.
C₁V₁ = C₂V₂; Vdiluent = V₂ − V₁- C₁ — Stock concentration
- Measured starting nucleic-acid mass concentration (ng/µL)
- V₁ — Stock volume
- Volume transferred from stock (µL)
- C₂ — Target concentration
- Desired final mass concentration (ng/µL)
- V₂ — Final volume
- Total volume after dilution (µL)
Dilute DNA from 100 to 10 ng/µL
Prepare 100 µL at 10 ng/µL from a 100 ng/µL stock.
- Stock
- 100 ng/µL
- Target
- 10 ng/µL
- Final volume
- 100 µL
- V₁ = 10 × 100/100 = 10 µL
- Diluent = 100 − 10 = 90 µL
Result: Combine 10 µL stock with 90 µL compatible diluent.
The final solution contains the same nucleic-acid amount as the transferred stock aliquot.
Understanding your results
The recipe is arithmetic, not a handling protocol
Choose nuclease-free, chemically compatible diluent and handling conditions using an approved laboratory procedure.
- Equal stock and target concentrations require zero diluent.
- Very small calculated stock volumes may need an intermediate dilution.
- Mass concentration is not molar concentration.
- Final accuracy depends on concentration measurement and pipetting performance.
Assumptions
- Stock and target use the same mass-concentration units and analyte basis.
- Nucleic acid is uniformly mixed and stable during preparation.
- Volumes are sufficiently additive for the intended precision.
Limitations
- Does not convert mass concentration to molarity or account for sequence length.
- Does not assess purity ratios, degradation, recovery, adsorption, or pipette uncertainty.
- Does not specify diluent composition or biosafety practices.
Common mistakes
- Confusing ng/µL with nM or µM.
- Adding final volume of diluent instead of subtracting stock volume.
- Using an impractically small transfer volume.
- Assuming measured absorbance represents pure intact nucleic acid.
Practical use cases
Sample normalization
Calculate equal target mass concentrations before a downstream workflow.
Working solutions
Prepare a lower-concentration aliquot from a measured DNA or RNA stock.
Frequently asked questions
Can dilution create a concentration above the stock?
No. That requires concentration or a stronger stock, not addition of diluent.
Is ng/µL the same as nM?
No. Converting mass concentration to molarity requires molecular weight, which depends on nucleic-acid length and composition.
What if the stock volume is below my pipette range?
Use a validated intermediate dilution or a larger final volume rather than relying on an inaccurate transfer.
Sources and review
- Molarity and Dilution — OpenStax Chemistry 2e. Accessed 2026-07-13.
Reviewed 2026-07-13.