Geometric Mean Calculator
Find the geometric mean of a list of numbers and compare it with the harmonic, arithmetic and quadratic (RMS) means. Switch to percentage changes to get the true average growth rate of returns, prices or populations, with the working shown step by step.
Separate with commas, spaces or new lines. For growth rates, enter each period's % change (e.g. 10 for +10%, -5 for −5%).
How to use the Geometric Mean Calculator
- Choose the input type: plain values, or percentage changes per period.
- Enter your numbers separated by commas, spaces or new lines.
- Read the geometric mean (or average growth rate) at the top.
- Compare it with the other means in the results and the chart.
- Follow the steps or copy the results.
The four classical means
| Mean | Formula | For 2, 8, 4, 16, 32 | Typical use |
|---|---|---|---|
| Harmonic | n ÷ Σ(1/x) | 5.1613 | Average speeds, rates, ratios |
| Geometric | (Π x)^(1/n) = exp(Σ ln x ÷ n) | 8 | Growth rates, returns, indices |
| Arithmetic | Σx ÷ n | 12.4 | Everyday averages, totals |
| Quadratic (RMS) | √(Σx² ÷ n) | 16.5167 | Errors, signals, magnitudes |
For positive values the means are always ordered HM ≤ GM ≤ AM ≤ QM. They are all equal only when every value is the same.
Arithmetic vs geometric average returns
| Returns | Arithmetic average | Geometric average | 100 becomes |
|---|---|---|---|
| +50%, −50% | 0% | −13.40% | 75 |
| +10%, +10%, +10% | 10% | 10% | 133.10 |
| +100%, −50% | 25% | 0% | 100 |
| +20%, −10%, +5% | 5% | 4.28% | 113.40 |
The geometric average is the constant rate that, compounded each period, gives the same end result. This is why investment performance and compound annual growth rates (CAGR) use it.
Frequently asked questions
What is the geometric mean?
The geometric mean of n positive numbers is the nth root of their product: GM = (x₁ × x₂ × … × xₙ)^(1/n). For 2, 8, 4, 16 and 32 the product is 32,768 and the 5th root is 8. It is the right average for quantities that multiply together, such as growth factors and ratios.
How do I calculate an average growth rate from yearly returns?
Convert each % change to a factor (1 + r/100), take the geometric mean of the factors and subtract 1. Returns of +50% and −50% give factors 1.5 and 0.5; their geometric mean is √0.75 ≈ 0.866, an average of −13.4% per period, which matches the real loss from 100 to 75.
Why is the geometric mean smaller than the arithmetic mean?
For positive numbers the inequality HM ≤ GM ≤ AM ≤ QM always holds, with equality only when all the values are equal. The more spread out the numbers are, the bigger the gap between the arithmetic and geometric means.
When should I use the harmonic mean?
Use the harmonic mean, n ÷ Σ(1/x), to average rates over equal amounts of something, such as speeds over equal distances or price-earnings ratios. Driving one leg at 60 km/h and an equal leg at 40 km/h gives an average speed of 48 km/h, not 50.
Can the geometric mean be calculated with zero or negative numbers?
Not in the usual sense. A zero makes the product, and therefore the geometric mean, zero, and negative values can make the root undefined. For growth data, use percentage changes, which are converted to positive factors as long as no change is −100% or worse.
What is the quadratic mean (RMS)?
The quadratic mean, or root mean square, is √(Σx² ÷ n). It weights large values more heavily and is used for alternating currents, errors (RMSE) and other quantities where the size of a value matters regardless of sign.