Education

Portfolio and Backtest Metrics, Explained: The Complete Guide

A plain-language guide to the metrics behind portfolio and strategy analysis: risk-adjusted returns, drawdown, factors, backtesting, and the market data behind them.

Almost every argument about an investment strategy comes down to a handful of numbers: how much it returned, how rough the ride was, and whether the return was worth the risk. This guide is a map of those numbers. Each entry explains one metric or method in plain language, including the part most guides skip, which is what the number does not tell you.

Use it as a reference. You do not need to read it in order, and no single metric here is the answer on its own.

Start with three questions

Almost all portfolio analysis is an attempt to answer three questions, and it helps to know which one you are asking before you pick a metric.

  • How much did it make? Return measures such as CAGR, rolling returns and XIRR.
  • How bad did it get? Risk measures such as maximum drawdown, volatility and downside deviation.
  • Was the return worth the risk? Risk-adjusted measures such as Sharpe, Sortino, Calmar, Treynor and the Information Ratio.

A fourth question sits underneath all of them: would you actually have known this at the time? That is the point-in-time problem, and it is why point-in-time data matters and why lookahead bias quietly ruins otherwise careful work.

Risk-adjusted return ratios

The measures that combine return and risk into a single number, and disagree with each other in useful ways.

Risk and drawdown

What the ride actually felt like, which is usually what decides whether an investor stays invested.

Measuring returns

Return looks like the simplest thing to compute and is quietly full of traps.

Trade and turnover statistics

The metrics that describe how a strategy behaved trade by trade.

Portfolio-level analytics

Looking at the whole book rather than one position at a time.

Scenario and stress analysis

Testing a portfolio against conditions that have not happened yet.

Backtesting

Everything about testing a rule against history, honestly.

Restatements deserve a special mention here, because they quietly corrupt any test built on fundamentals. See why restatements break models and why point-in-time databases are hard.

Factor investing

The systematic sources of return that sit underneath most rule-based strategies.

Systematic investing

Market flows, breadth and events

The market data that most rule-based work eventually reaches for.

Indices and benchmarks

Portfolio construction and operations

Funds and vehicles

The habit that matters more than any metric

Every number on this page is a summary of the past under a set of assumptions. The assumptions are where the work is. Was the data as it stood at the time, or as it was later restated? Were costs included? Were the companies that failed still in the sample? Change any of those and most of the metrics above change with them.

That is the honest position: metrics are a language for describing what happened, not a machine for predicting what will. Learn to read them, and learn where each one is silent.

This article is educational. Altys Labs is not a registered research analyst or investment adviser, and nothing here is investment advice or a recommendation to buy, sell, or hold any security.

Frequently asked questions

Which portfolio metrics actually matter?

It depends on the question you are asking. Use a return measure such as CAGR to describe growth, a risk measure such as maximum drawdown or volatility to describe the ride, and a risk-adjusted measure such as Sharpe or Calmar to combine the two. No single number is sufficient, and any metric read alone can mislead.

What is the difference between a risk metric and a risk-adjusted return metric?

A risk metric describes only the danger, for example volatility or maximum drawdown. A risk-adjusted return metric divides return by some measure of that danger, so it tells you how much return you earned per unit of risk taken. Sharpe, Sortino, Calmar, Treynor and the Information Ratio are all risk-adjusted measures that differ in which risk they use.

Why do backtest results often fail to repeat in practice?

Common reasons are costs and slippage that were not modelled, survivorship bias in the data, overfitting to the sample, and a change in market regime. A backtest is evidence about the past under a set of assumptions, not a forecast, and reading it that way is the single most useful habit.