A260 Calculator (DNA/RNA Concentration & Purity)

Quick answer

If you have a NanoDrop or spectrophotometer reading, this page tells you the DNA/RNA concentration, A260/280, A260/230, and optional total yield in one pass.

Useful for quick sample triage before qPCR, cleanup, library prep, or copy-number conversion.

How to use (3 steps)

Select nucleic acid type (dsDNA/RNA, etc.) and enter A260/A280/A230.
If measured with dilution, enter the dilution factor (no dilution = 1).
Concentration and ratios appear automatically. Add volume to see total amount.

Typical use cases: checking whether an extraction is clean enough, deciding whether to remeasure after blank correction, or preparing a hand-off to qPCR/NGS workflows.

A260 factors and ratio guides vary by sample and conditions. They are shown as references; confirm with your assay.

Input (type, A260/A280/A230, dilution)

Example (preset)

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Nucleic acid type

Factor F (µg/mL per A260=1)

dsDNA=50 and RNA=40 are common guides. Use a custom factor if needed.

A260 (required)

A280 (optional)

A230 (optional)

Dilution preset

Dilution factor D (no dilution = 1)

Calculate total amount from volume

Volume preset

Volume (µL)

Blank correction (optional)

Many instruments already apply blank correction. Enable only if needed.

Use blank correction

Blank A260

Blank A280

Blank A230

Results (concentration & ratios)

With JavaScript enabled, the first example loads automatically and shows concentration, A260/280, and A260/230. Enter your own readings to replace it.

Concentration (ng/µL)

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Concentration (µg/mL)

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A260/280

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A260/230

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Dilution factor

—

A260/280 guide: — A260/230 guide: —

About ratio guides (reference)

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1 µg/mL = 1 ng/µL (same numeric value).

Ratio interpretation depends on the assay; this calculator does not make definitive judgments.

Export (copy / CSV / LaTeX / share URL)

How it’s calculated

Concentration (µg/mL) = A260 × factor × dilution (dsDNA=50, RNA=40 are guides)
A260/280 = A260 ÷ A280 (A280 ≠ 0)
A260/230 = A260 ÷ A230 (A230 ≠ 0)
Entering volume calculates total amount (ng/µg)

FAQ

Is the dsDNA factor of 50 fixed?

It is a commonly used guide, but it can vary by sample and conditions. Use a custom factor if needed.

What do A260/280 and A260/230 indicate?

They are often cited as guides for protein or salt/solvent contamination, but they are not definitive.

What does entering volume show?

It calculates the total amount (ng/µg) in the tube from the concentration.

Do I need blank correction?

Many instruments correct internally. Enable it only if needed.

Is the data sent anywhere?

All calculations run in your browser; data is not sent.

What to do after you get an A260 result

Use A260 as a first-pass check

A260 is useful for a fast concentration estimate and a rough purity check, especially when you need an immediate decision about dilution, cleanup, or whether a sample is ready for the next step. Treat it as a screening measurement, not as the final truth for every downstream workflow.

Check concentration and ratios together

A sample can show a reasonable concentration while still having unstable A260/280 or A260/230 ratios. Read all three values together. If concentration looks usable but the ratios move a lot after blank correction or another dilution, the sample may need cleanup or a repeat measurement before you trust the number.

When to confirm with another method

If you are preparing libraries, normalizing qPCR inputs, or comparing valuable low-yield samples, it is often worth confirming concentration with a fluorescence-based assay or another method used in your lab. That is especially true when A260 and the expected yield disagree.

Practical repeat-check workflow

A practical sequence is: measure once, record the raw absorbance values, try blank correction only if your instrument did not already apply it, then compare one alternate dilution. If the corrected concentration stays stable across those checks, the result is usually good enough to move forward.

Hand-off to downstream tools

Once the concentration is credible, convert it to molarity or copies for planning, then move to qPCR analysis or library normalization. Keeping that order reduces rework because you only pass forward measurements that already survived a quick plausibility check.

Quick next-step guide

If concentration looks plausible but A260/280 or A260/230 shifts a lot, repeat the measurement or review blank correction before you report the value.
If the sample is low-yield or operationally important, confirm concentration with a fluorescence-based assay before making a final dilution plan.
If the sample is acceptable and you need expression analysis, continue to the qPCR standard curve or ΔΔCt workflow.
If the sample is acceptable and you are preparing libraries or pooling, convert to nM first and then use the NGS library concentration workflow.

Related tools

DNA/RNA converter (ng/µL ↔ nM ↔ copies)
Convert the A260 concentration into molarity or copy number before planning dilutions or assay inputs.
qPCR standard curve
Use it when you need efficiency, slope, and sample quantification after checking nucleic-acid input quality.
ΔCt / ΔΔCt (relative expression)
Move here after concentration and RNA quality checks when you are comparing expression across conditions.
NGS library concentration (ng/µL → nM)
Useful when the A260 result is only the starting point and you need library normalization or pooling.
Primer Tm calculator
Use alongside qPCR planning to check primer annealing conditions after you confirm template concentration.

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