How to Read an ETF Factsheet: The Numbers That Actually Matter

Every ETF comes with a factsheet - a one or two-page summary published by the fund provider. For most passive investors, it goes unread. That is a mistake. The factsheet contains the numbers that determine whether two apparently identical funds are actually the same, and whether the one you hold is quietly eroding your returns.

This article explains the main statistics you will encounter, what they mean, and what counts as good or bad.

Ongoing Charge Figure (OCF)

The OCF - sometimes called the Total Expense Ratio (TER) or expense ratio - is the annual cost of owning the fund, expressed as a percentage of your investment. A 0.20% OCF means you pay £20 per year on a £10,000 holding.

It covers management fees, administration, and custody costs. It does not cover trading costs or stamp duty when the fund rebalances - which is why the OCF alone understates the true cost of ownership.

What is good? For a broad index ETF tracking the S&P 500 or MSCI World, anything under 0.10% is competitive. FTSE All-World ETFs typically run between 0.15% and 0.25%. Above 0.50% for a passive fund is hard to justify.

The compounding effect of fees is severe. At 7% gross return over 30 years, a 0.07% OCF versus a 0.50% OCF on a £10,000 investment produces a difference of over £10,000 in final value.

Tracking Difference and Tracking Error

These two are often confused.

Tracking difference is the gap between the fund's actual annual return and the return of the index it tracks. If the S&P 500 returned 10.0% and your ETF returned 9.85%, the tracking difference is −0.15%. A negative tracking difference (fund lagging index) is normal and expected - the OCF accounts for most of it. Some ETFs actually beat their index through securities lending income, producing a positive tracking difference.

Tracking error is the volatility of that gap over time - how consistently the fund tracks its index. A fund with a low tracking error replicates the index reliably day to day, even if there is a persistent small gap. A high tracking error suggests the fund is drifting - potentially due to sampling methods, cash drag, or poor replication.

What is good? For a physically replicated index ETF, tracking error below 0.10% annually is excellent. Tracking difference close to or better than zero is ideal.

Beta

Beta measures how much the fund moves relative to its benchmark market. A beta of 1.0 means the fund moves in lockstep with the market. A beta of 1.2 means it amplifies market moves by 20% in both directions. A beta of 0.8 means it is 20% less volatile than the market.

For a plain index ETF, beta should be very close to 1.0 - that is the whole point. A significant deviation suggests the fund is not tracking as expected, or is using leverage.

Beta also tells you something about sector-tilted ETFs. A clean energy ETF might have a beta above 1.5 against the broad market - higher potential return, but amplified drawdowns.

Alpha

Alpha measures return in excess of what beta alone would predict - the fund's value added (or destroyed) after adjusting for market exposure.

For a passive index ETF, you should expect alpha close to zero. By definition, an index fund is not trying to add alpha - it is trying to capture the market return at minimal cost. Consistently positive alpha in a passive fund is usually explained by securities lending income or favourable dividend tax treatment, not skill.

Where alpha matters is when comparing active funds. A consistently negative alpha after fees is the clearest possible signal that an active manager is destroying value.

Sharpe Ratio

The Sharpe ratio measures risk-adjusted return: how much excess return you receive per unit of volatility taken.

Sharpe ratio = (fund return − risk-free rate) ÷ standard deviation of returns

A higher Sharpe ratio is better. A ratio above 1.0 is considered good; above 2.0 is exceptional. The ratio is most useful when comparing two funds with similar objectives - it tells you which delivered more return per unit of risk, rather than raw return alone.

Be cautious of Sharpe ratios calculated over short periods. A fund that happened to run during a bull market will look excellent. Always check the time period used.

Standard Deviation (Volatility)

Standard deviation quantifies how much the fund's returns vary over time. A higher standard deviation means wilder swings - larger gains in good years, larger losses in bad ones.

For context, the S&P 500 has historically had an annualised standard deviation of around 15-17%. A broad global equity ETF should sit in a similar range. A bond ETF might be 4-7%. A sector ETF or leveraged product can exceed 30%.

Standard deviation is not inherently bad - volatility is the price of long-term equity returns. But understanding it helps you hold your nerve during drawdowns and avoid selling at the worst moment.

Putting It Together: What to Check Before Buying

When evaluating any ETF, run through this sequence:

1. OCF - is it competitive for this asset class?
2. Tracking difference - does the fund faithfully replicate its index?
3. Beta - is it what you expect for this strategy?
4. Sharpe ratio - compared to peers over the same period, is risk being rewarded?
5. Standard deviation - does the volatility fit your time horizon and temperament?

Two ETFs tracking the same index can differ meaningfully on all of the above. The factsheet is where those differences live.

For a broader look at how to choose between funds once you understand the numbers, see how to choose a low-cost index fund.

Contents

• Ongoing Charge Figure (OCF)
• Tracking Difference and Tracking Error
• Beta
• Alpha
• Sharpe Ratio
• Standard Deviation
• Putting It Together
• Frequently Asked Questions

Frequently Asked Questions

What is the most important number on an ETF factsheet?

For a passive index fund, the Ongoing Charges Figure (OCF) is the starting point - it is the annual cost deducted from your returns. But the tracking difference is often more revealing: it shows whether the fund is actually delivering the index return minus fees, or whether additional costs are creating a larger gap. Look at both together.

What is the difference between tracking difference and tracking error?

Tracking difference is the gap between the fund's annual return and its benchmark's return - it tells you how much you under- or outperformed the index. Tracking error is the volatility of that gap over time - it tells you how consistently the fund tracks its index day to day. A fund can have a persistent tracking difference (expected) but should have a low tracking error (consistent replication).

What should beta be for a simple index ETF?

Very close to 1.0. A beta of 1.0 means the fund moves in lockstep with its benchmark. A significant deviation above or below 1.0 suggests the fund is leveraged, is using synthetic replication with unexpected exposure, or is not tracking as expected. For a standard global equity tracker, beta outside the range of 0.95 to 1.05 warrants investigation.

Is a high Sharpe ratio always good?

A higher Sharpe ratio indicates more return per unit of volatility taken, which is generally preferable. But be cautious about short measurement periods: a fund that ran through an extended bull market will show an inflated Sharpe ratio that does not reflect its risk-adjusted performance over a full cycle. Always check the period the ratio covers.

Do ETF factsheet numbers change over time?

Yes. OCFs are updated periodically and can change as providers reprice their funds competitively. Tracking difference and error are calculated from historical data and will shift with market conditions. Always check the factsheet date and look for the most recent version from the fund provider's website before making a final decision.

Further Reading:

The ETF Book - Richard Ferri - The most comprehensive guide to ETF mechanics, selection, and portfolio construction available to retail investors. Covers everything on a factsheet and much more. (Affiliate link - we may earn a small commission at no extra cost to you.)