RSD Calculator: Relative Standard Deviation (%RSD / %CV)

RSD Calculator

Relative standard deviation (%RSD / %CV)

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Relative Standard Deviation (RSD), also called the coefficient of variation (%CV), expresses the standard deviation as a percentage of the mean — making it easy to compare variability between data sets with different units or scales.

Formula: %RSD = (Standard Deviation ÷ Mean) × 100. Lower %RSD means tighter, more precise data — common in analytical chemistry, %RSD under 2% is considered highly precise.

Calculate Using

Data Set

Separate values with commas, spaces, or new lines.

Standard Deviation Type

Sample (n − 1) — most common Population (n)

📊 Your Result

%RSD (Coefficient of Variation)

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Enter a data set to calculate

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Mean

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Standard Deviation

Count (n)

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Sum

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Minimum

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Maximum

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Variance

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Range

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Calculation

A standard deviation of 5 means very different things depending on whether your mean is 10 or 10,000, relative standard deviation solves that by expressing variability as a percentage of the mean, making precision comparable across data sets with completely different scales or units.

How to use this RSD calculator

Choose your input mode: Data Set (paste raw values) or Standard Deviation & Mean (enter both directly).
If using a data set, paste your values separated by commas, spaces, or new lines, and choose Sample or Population standard deviation.
Review your %RSD (Coefficient of Variation), along with Mean, Standard Deviation, Count, Sum, Minimum, Maximum, Variance, and Range.

What this RSD calculator does

Relative Standard Deviation (RSD), also called the coefficient of variation (%CV), expresses the standard deviation as a percentage of the mean. This normalization is what makes it possible to compare the precision or variability of two data sets that use different units or operate at very different magnitudes.

%RSD = (Standard Deviation ÷ Mean) × 100

Sample vs population standard deviation

When calculating from a raw data set, this calculator lets you choose between sample standard deviation (dividing by n−1), the more common choice when your data represents a sample drawn from a larger population, and population standard deviation (dividing by n), used when your data set represents the entire population of interest rather than a sample.

Why %RSD matters in analytical chemistry and lab work

In fields like analytical chemistry, %RSD is a standard measure of measurement precision and repeatability, a %RSD under 2% is generally considered highly precise. However, acceptance criteria for %RSD vary significantly by field, application, and regulatory context, so always check your specific field’s acceptance criteria before using a %RSD result for regulatory or quality-control decisions rather than relying on a generic benchmark.

Frequently asked questions

What’s the difference between RSD and standard deviation?

Standard deviation is an absolute measure of spread in the same units as your data, while RSD (relative standard deviation) expresses that spread as a percentage of the mean, making it possible to compare variability across data sets with different units or scales.

Should I use sample or population standard deviation?

Use sample standard deviation (n−1) when your data is a sample drawn from a larger population, this is the more common choice and the default. Use population standard deviation (n) only when your data set represents the entire population you’re interested in, not just a sample of it.

What counts as a “good” %RSD?

In analytical chemistry, %RSD under 2% is generally considered highly precise, but acceptance criteria vary significantly by field and application. Check your specific field’s standards before using a %RSD result for regulatory or quality-control decisions.