Alpha, Beta and Sharpe: Mutual Fund Ratios Explained
Alpha, beta and the Sharpe ratio answer three separate questions about a mutual fund: did the manager add value, how hard does the fund swing with its index, and how much return did you get for the bumpiness you sat through. Two funds can report the same three year return and score very differently on all three.
These are risk-adjusted measures: they judge a fund’s return against the risk it took to produce it, not in isolation. Factsheets print them in a small grey box most investors skip. That box often says more than the headline return.
What follows: what each ratio measures, a side by side calculation on two hypothetical large cap funds, and where these numbers quietly mislead.
Why the headline return hides the interesting part
A fund returning 15% a year over three years looks better than one returning 13%. But suppose the first dropped 34% in a bad quarter and the second dropped 19%. If you panic-redeemed that quarter, the 15% never reached you.
Risk ratios put that difference on paper. All of them are calculated against a benchmark index and a risk free rate, so change the benchmark and the numbers change. Checking that the fund is measured against a sensible mutual fund benchmark therefore comes first. A mid cap fund flattered by a large cap index is not showing skill, it is showing a labelling error.
Beta: how hard does the fund swing with its index?
Beta compares the fund’s movement to the benchmark’s movement. The benchmark is always 1.0.
- Beta of 1.0: the fund moves roughly in line with the index.
- Beta of 1.2: for every 10% the index moves, the fund has tended to move about 12%, in both directions.
- Beta of 0.8: about 8% for a 10% index move. Gentler down, slower up.
Beta is not a quality score. A low beta fund is not safer in any absolute sense, only less reactive to that index. An index fund sits near 1.0 by design, and a fund holding heavy cash can show low beta purely because of the cash.
Alpha: the part the manager added
Alpha is the return delivered above what beta alone would predict. Positive alpha suggests the manager added something. Negative alpha means the fund fell short of what its risk exposure should have produced.
The common version, Jensen’s alpha:
Expected return = risk free rate + beta x (benchmark return - risk free rate)
Alpha = actual return - expected return
Two cautions. Alpha is measured after the expense ratio, so a costly fund starts in a hole. And a scheme’s direct plan shows better alpha than its regular plan for no reason but cost, which is one more argument for understanding direct versus regular plans.
Sharpe ratio: return per unit of risk
Sharpe divides the return earned above a risk free rate by the fund’s standard deviation.
Sharpe ratio = (fund return - risk free rate) / standard deviation of fund returns
A higher Sharpe means more reward per unit of wobble. There is no absolute pass mark, so it only means something across funds in the same category, over the same period, against the same risk free rate.
Standard deviation, the input everyone ignores
Standard deviation measures how widely returns scattered around their own average. A fund averaging 12% with a deviation of 8% mostly landed between 4% and 20%. Raise the deviation to 20% and the same average covers a far rougher ride.
Sortino, for people who only fear losses
Sharpe penalises upside and downside volatility equally, which is odd. Sortino counts only downside deviation, so between two funds with similar Sharpe ratios, the higher Sortino had fewer painful stretches.
Worked example: two large cap funds side by side
Suppose the risk free rate is 6.5% and the benchmark returned 12.0% a year. Two funds report the following.
| Measure | Fund A | Fund B |
|---|---|---|
| 3 year annualised return | 15.0% | 13.2% |
| Standard deviation | 16.0% | 11.0% |
| Beta | 1.15 | 0.85 |
| Expected return from beta | 12.83% | 11.18% |
| Alpha | +2.17% | +2.02% |
| Sharpe ratio | 0.53 | 0.61 |
The arithmetic, so you can repeat it on any factsheet.
Fund A expected return: 6.5 + 1.15 x (12.0 – 6.5) = 6.5 + 6.325 = 12.83%. Actual was 15.0%, so alpha is 2.17%. Sharpe: (15.0 – 6.5) / 16.0 = 0.53.
Fund B expected return: 6.5 + 0.85 x 5.5 = 6.5 + 4.675 = 11.18%. Actual was 13.2%, so alpha is 2.02%. Sharpe: (13.2 – 6.5) / 11.0 = 0.61.
Read that carefully. Fund A won on return and alpha; Fund B won on Sharpe, producing almost the same edge with two thirds of the volatility. Neither is the automatic answer. A fifteen year horizon can live with Fund A. Someone who needs the money in four years, or who has panic-redeemed before, is better served by Fund B. This is the core of comparing two mutual funds properly.
On Rs 10 lakh, that 1.8 point annual gap compounds to roughly Rs 60,000 extra over three years, bought with wider drawdowns.
What do these ratios refuse to tell you?
They are backward looking, computed from past monthly returns. A manager who left last quarter still shows up in the alpha.
They need history. Ratios on fourteen months of data are noise. Three years is a floor, five is better.
They assume returns behave normally, which they do not in a crash, so standard deviation understates the worst week.
And they ignore what sits inside the portfolio. A fund can post a tidy Sharpe while holding illiquid small caps that would be hard to sell in a stressed market. The SEBI mandated riskometer, refreshed monthly, plus the portfolio disclosure, cover that gap better, especially read alongside mutual fund risk ratings.
How should a beginner actually use them?
- Fix the category first. Compare flexi cap with flexi cap, never with a debt fund.
- Confirm the benchmark and period are identical across the funds you are lining up.
- Use beta to check you are not stacking the same aggressive tilt twice.
- Use Sharpe to break a tie between funds with similar returns.
- Treat alpha as a hypothesis about the manager, then check tenure and strategy consistency.
- Ignore all four if the fund has under three years of history.
Risk note: these ratios describe the past. An attractive Sharpe does not stop a fund losing a large share of its value in a market fall. Equity funds carry market risk that no factsheet removes.
Frequently Asked Questions
What is a good Sharpe ratio for an Indian equity mutual fund?
There is no fixed threshold, and any figure quoted as universal is guesswork. Sharpe depends on the period, so a whole category can look excellent in a bull run and poor in a flat year. The only useful reading is relative: compare funds in the same category over the same window, using the category median as reference.
Can a fund have negative alpha but still make money?
Yes, often. If the index gained 14% and the fund gained 11% with a beta near 1.0, you made money while alpha was negative. Alpha measures performance against expectations set by risk taken, not against zero. Positive returns with negative alpha mean the index did the work.
Where do I find alpha, beta and Sharpe for a scheme?
The AMC’s monthly factsheet carries them near the portfolio summary, with the risk free rate and benchmark used. Rating portals show them too, but assumptions differ. If two sources disagree, check which benchmark and risk free rate each applied before assuming one is wrong.
Do these ratios work for debt funds?
Partly. Standard deviation and Sharpe can be computed, but a debt fund’s main risks are credit quality and interest rate sensitivity, which these ratios miss. Modified duration, average maturity and the credit rating profile tell you far more than beta ever will.
Does a low beta fund protect me in a market crash?
It usually falls less than the index, but it still falls. Beta is an average tendency measured over calm and volatile periods together, and correlations rise in a crash, so low beta funds often behave like the index precisely when you did not want that.
Key Takeaways
- Beta measures sensitivity to the benchmark, alpha measures return above what that beta predicted, Sharpe measures return above the risk free rate per unit of volatility.
- Jensen’s alpha: expected return equals risk free rate plus beta times the benchmark’s excess return, subtracted from the actual return.
- Higher return with a lower Sharpe means the extra gain was bought with extra volatility, which suits only investors who will not redeem early.
- No ratio is valid without the correct benchmark, an identical period and at least three years of data.
- Expense ratio drags alpha directly, so a direct plan always scores better than the regular plan of the same scheme.
- These numbers miss liquidity and concentration risk, so read the portfolio and the riskometer too.
