Sortino Ratio Calculator

The Sortino ratio calculator measures the risk-adjusted return of an investment, but unlike the Sharpe ratio, it penalises only downside volatility rather than all volatility. It is used by portfolio managers and sophisticated investors who recognise that upside variability is not a genuine risk. A higher Sortino ratio indicates better risk-adjusted performance relative to harmful, downside risk.

How to Use the Sortino Ratio Calculator

1. Enter the portfolio's average annual return as a percentage.
2. Input the minimum acceptable return (MAR), also called the target return. This is often set to zero or to the risk-free rate.
3. Enter the downside deviation: the standard deviation of returns that fall below the MAR.
4. The calculator divides the excess return by the downside deviation and displays the Sortino ratio.
5. Compare the result to other portfolios or to the Sharpe ratio to see how the perspective on risk changes.

The Formula

Sortino Ratio = (Portfolio Return minus Minimum Acceptable Return) divided by Downside Deviation

Where:

Portfolio Return is the mean annual return of the investment over the measurement period.

Minimum Acceptable Return (MAR) is the threshold return below which you consider a result a loss. This is often set to zero (no loss), to inflation, or to the risk-free rate.

Downside Deviation is the standard deviation of only those returns that fall below the MAR. It is calculated by taking all periods where return was below the MAR, squaring each shortfall, averaging those squared values, then taking the square root. Positive returns above the MAR are excluded from this calculation.

The key distinction from the Sharpe ratio is that months where the fund returned 20% above target are not counted as risk in the Sortino ratio, whereas they inflate the standard deviation (and reduce the Sharpe ratio).

Real-World Example

A fund produces the following annual returns over 5 years: 15%, minus 8%, 22%, minus 3%, 10%.

Average return = (15 minus 8 plus 22 minus 3 plus 10) divided by 5 = 36 divided by 5 = 7.2%.

The MAR is set to 0%. Only the years with negative returns count toward downside deviation.

Shortfalls below MAR: minus 8% and minus 3%.

Squared shortfalls: 64 and 9. Average squared shortfall = (64 plus 9) divided by 5 = 73 divided by 5 = 14.6 (note: divide by total periods, not just negative periods). Downside deviation = square root of 14.6 = approximately 3.82%.

Sortino Ratio = (7.2 minus 0) divided by 3.82 = 1.88.

For comparison, the standard deviation of all returns would be higher, and the Sharpe ratio would be lower, because it would also count the high-return years as volatility.

Sortino Ratio vs Sharpe Ratio

The Sortino ratio is considered a more realistic measure for strategies that naturally have asymmetric return distributions, such as trend-following funds, covered call strategies, or any portfolio that experiences occasional large positive returns.

For a fund with mostly consistent returns and few extreme outliers, the Sharpe and Sortino ratios will produce similar rankings. The difference becomes significant when comparing strategies like:

A momentum fund with frequent large positive months and occasional sharp drawdowns (high Sharpe, moderate Sortino).

A low-volatility fund with steady small gains and rare but sharp losses (similar Sharpe and Sortino).

An options-selling strategy with many small wins and rare large losses (good Sharpe ratio but potentially poor Sortino ratio, revealing hidden tail risk).

As a benchmark, a Sortino ratio above 2.0 is generally considered good for an equity portfolio. Values above 3.0 are excellent.

Frequently Asked Questions

What is the difference between the Sortino ratio and the Sharpe ratio? Both measure risk-adjusted return, but the Sharpe ratio uses total standard deviation (including upside volatility), while the Sortino ratio uses only downside deviation. The Sortino ratio is considered a better measure for investors who are concerned only about losing money rather than experiencing any form of return variability.

What minimum acceptable return should I use? Common choices include zero (you consider any loss unacceptable), the risk-free rate (you want to at least beat cash), or a specific target such as inflation or a benchmark return. The choice affects the ratio significantly, so always compare Sortino ratios calculated with the same MAR.

Is a higher Sortino ratio always better? A higher Sortino ratio generally indicates better risk-adjusted performance on a downside basis. However, it should always be considered alongside the absolute return level, the time period measured, and other risk metrics. A strategy can achieve a high Sortino ratio by avoiding volatility altogether, which may mean sacrificing too much return.

What is a good Sortino ratio for an equity fund? There is no universal standard, but values above 1.0 are generally considered acceptable, above 2.0 good, and above 3.0 excellent. These benchmarks are broadly similar to Sharpe ratio norms. Comparing within the same asset class and time period is more meaningful than applying a single absolute threshold.

Year by year, the shortfall table

The downside deviation is built from a shortfall for every period in the sample, not only the periods that fell short. A period above the minimum acceptable return contributes a shortfall of zero, and that zero still counts in the denominator.

Here is the five-year series from the worked example above, with a minimum acceptable return of zero.

The two negative years contribute 64 and 9, so the sum of squared shortfalls is 73. Dividing by the five periods gives 14.6, and the square root is 3.8210. The mean return is 7.2 percent, so the ratio is 7.2 divided by 3.8210, which is 1.8843.

Two conventions for the downside deviation

The definition of the downside deviation is an expectation. An expectation is an average over every period in the sample, which is why the divisor is 5 in the arithmetic above rather than the 2 negative years. Some implementations divide by the count of downside periods instead. Both conventions appear in published comparisons, and they do not produce the same number.

The second convention inflates the deviation by a factor of 1.58 on this sample, and it lowers the ratio from 1.8843 to 1.1918. Nothing about the portfolio changed. A ratio quoted without its convention is therefore ambiguous, and a ratio compared against a published benchmark is only meaningful if both were built the same way. The convention that divides by all periods is the one that matches the definition of a semi-deviation, and it is the one to use when the result has to be comparable with a standard measure.

The same five years under the Sharpe ratio

The Sharpe ratio uses the standard deviation of every return, so the two high years count as risk alongside the two low ones.

The mean return is 7.2 percent. The five deviations from that mean are plus 7.8, minus 15.2, plus 14.8, minus 10.2 and plus 2.8. Their squares are 60.84, 231.04, 219.04, 104.04 and 7.84, which sum to 622.8. Dividing by 5 gives a variance of 124.56 and a standard deviation of 11.1606. Dividing by 4 instead gives a variance of 155.7 and a standard deviation of 12.4780.

The two measures disagree by a wide margin on this sample. The downside deviation is 3.8210 against a total deviation of 11.1606, so the Sortino ratio comes out 2.92 times the Sharpe ratio. The reason is that the two large positive years inflate the standard deviation while contributing nothing to the downside deviation. On a sample with no large positive outliers the two measures converge, which is exactly the condition the next section on the minimum acceptable return is about.

What the minimum acceptable return does to the result

The minimum acceptable return is a decision, not a measurement. Moving it changes both the numerator and the denominator, so the ratio moves more than most users expect.

The 5 percent row is easy to follow by hand. Raising the target to 5 percent brings two shortfalls into the calculation, one of 13 and one of 8, because the two negative years are now 13 and 8 below the target instead of 8 and 3. Their squares are 169 and 64, which sum to 233. Dividing by 5 gives 46.6, and the square root is 6.8264. The mean return is 2.2 percent above the target, so the ratio is 2.2 divided by 6.8264, which is 0.3223.

At an 8 percent target the mean return sits below the target and the ratio turns negative. A negative ratio does not mean the portfolio lost money. It means the portfolio failed to clear the target over the measurement period. Two portfolios compared against different targets are not comparable at all, which is the argument for printing the minimum acceptable return beside every ratio a report publishes.

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