What formula does the calculator use?

It uses concentration = A260 × dilution factor × DNA conversion constant ÷ path length in cm.

Which conversion constants are supported?

The calculator uses 50 µg/mL per OD for dsDNA and 33 µg/mL per OD for ssDNA.

Why is the dilution factor needed?

It converts the measured concentration of a diluted sample to the estimated concentration of the original sample.

How is total DNA yield calculated?

When sample volume is entered, total yield equals concentration in µg/µL multiplied by the elution volume in µL.

What does the linear-range check mean?

A260 values from 0.1 to 1.5 are marked within range; values above 1.5 are flagged for dilution and re-measurement.

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DNA Concentration Calculator (A260 Absorbance)

Beer–Lambert DNA quantitation: c = A260 × dilution factor × K / path length with 1 OD = 50 µg/mL dsDNA or 33 µg/mL ssDNA, plus ng/µL, total yield, and a 0.1–1.5 linear-range check. Derived from Marmur & Doty, Sambrook & Russell, Thermo Fisher NanoDrop notes. Educational use only.

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2 examples

Plasmid miniprep: A260 = 0.25, 1:10 diluted dsDNA

A 1:10 diluted plasmid miniprep reads A260 = 0.25 on a standard 1 cm cuvette. Concentration = 0.25 × 10 × 50 / 1 = 125 µg/mL = 125 ng/µL of dsDNA. The 100 µL elution therefore holds 125 × 0.1 = 12.5 µg total — a typical healthy miniprep yield, and the reading sits comfortably inside the 0.1–1.5 linear range.

{"result":"dsDNA concentration = 125 µg/mL (125 ng/µL); total 12.5 µg in 100 µL.","metadata":{"input":{"a260":0.25,"dnaType":"dsDNA","dilutionFactor":10,"pathLengthCm":1,"sampleVolumeUl":100},"result":{"constantUgMlPerOd":50,"concentrationUgMl":125,"concentrationNgUl":125,"totalUg":12.5,"measurementQuality":"within linear range (0.1–1.5)"}}}

ssDNA oligo prep: A260 = 1.8 warns to dilute

An undiluted single-stranded DNA prep reads A260 = 1.8 — above the ~1.5 upper edge of the linear range, so the detector may saturate and the value 1.8 × 1 × 33 / 1 = 59.4 µg/mL should be re-measured after further dilution. The example shows the constant swap (33 instead of 50) and how the tool flags out-of-range readings instead of silently trusting them.

{"result":"ssDNA concentration = 59.4 µg/mL (59.4 ng/µL); reading above the linear range — dilute and re-measure.","metadata":{"input":{"a260":1.8,"dnaType":"ssDNA","dilutionFactor":1,"pathLengthCm":1,"sampleVolumeUl":0},"result":{"constantUgMlPerOd":33,"concentrationUgMl":59.4,"concentrationNgUl":59.4,"totalUg":null,"measurementQuality":"above linear range — dilute sample"}}}

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6 options

SettingsAdjust formats, ranges, numbers, and modes.6

A260 AbsorbancenumberRequiredMeasured absorbance of the (diluted) sample at 260 nm, blanked against the elution buffer.DNA TypeselectRequireddsDNA uses 1 OD = 50 µg/mL; ssDNA uses 1 OD = 33 µg/mL.Dilution FactornumberRequiredSample-to-total dilution before measurement (1 = measured undiluted).Path Length (cm)numberRequiredCuvette path length (1 cm standard; microvolume readers may use 0.1–1 cm).Sample Volume (µL, optional)numberOptionalTotal elution volume in µL; enter 0 to skip the total-yield calculation.Decimal PlacesnumberOptional

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DNA Concentration Calculator (A260 Absorbance)

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Examples

1. Plasmid miniprep concentration and yield

2. ssDNA measurement above the linear range

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