Understand the relationship
The reasoning behind the result
A mass factor is not a molar extinction coefficient
This workflow uses an entered mass-concentration factor: the concentration in ng/µL corresponding to absorbance one at a 1 cm path. It is intentionally different from the molar coefficient in the Beer–Lambert tool.
The factor depends on the measured material and method. Examples demonstrate arithmetic with entered factors; the calculator does not infer a DNA/RNA composition, sequence, purity or universal factor from a sample name.
Normalize the optical path once
A260,1cm = A260/ℓcm
A value already normalized by an instrument to a 1 cm path uses ℓ = 1 here. A raw absorbance attached to a 0.1 cm path is divided by 0.1. Correcting an already-normalized reading again would overstate the concentration.
After path normalization, apply the entered factor and then the dilution correction. All three operations remain visible in the supporting results.
Concentration and recovered amount
massng = coriginal,ng/µL × Voriginal,µL
A concentrated small sample can contain less total material than a dilute large sample. Multiplying the original-sample concentration by its original volume gives the recovered mass represented by those inputs.
Absorbance-based amount does not establish molecular integrity or downstream functionality. Contaminants that absorb at the measured wavelength can also affect the estimate.
Follow the numbers
From diluted reading to recovered mass
- A260 = 0.2 at 1 cm, with entered factor 50 ng/µL, gives 10 ng/µL in the measured solution.
- A fivefold dilution correction gives 50 ng/µL in the original sample.
- At original volume 100 µL, total mass is 5,000 ng = 5 µg.
The concentration and total mass use the original sample after the dilution is reversed.
Quick guide
How to use this calculator
- Enter corrected A260 and the optical path attached to that reading.
- Enter the factor justified by the nucleic-acid type and measurement method.
- Enter dilution once and the volume of the original sample to calculate total mass.
Calculation method
Calculation and interpretation
Reconcile A260, path normalization, dilution and recovered nucleic-acid amount using the factor specified by your measurement method.
coriginal = (A260/ℓcm) × entered factor × dilution factor; total mass = coriginal × original volume
Worked example
From diluted reading to recovered mass
The concentration and total mass use the original sample after the dilution is reversed.
coriginal = (A260/ℓcm) × entered factor × dilution factor; total mass = coriginal × original volume
Supported inputs
Precision and limits
Measurement controls
Entered signals must have a suitable background correction and remain within the measurement system's established working range. Saturated or incompatible measurements cannot be repaired by a ratio.
Biological interpretation
A relative signal, absorbance ratio or calculated loading volume does not establish sample purity, gene expression, mechanism, statistical significance or experimental validity.
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