Ask most investors how their portfolio performed last year and they’ll say something like “I started with $50,000 and ended with $58,000, so I made 16%.” That math is right only if no money moved in or out during the year. Add a $10,000 contribution in March and the same ending balance suddenly means very different things about the portfolio’s actual performance. Getting this right matters for evaluating whether your investment strategy is working.
Simple Return: When It Works and When It Doesn’t
Simple return is the most straightforward calculation:
Simple Return = (Ending Value − Beginning Value) ÷ Beginning Value
This is accurate when no money enters or leaves the portfolio during the period. If you started with $100,000, made no contributions or withdrawals, and ended with $107,000, your return is exactly 7%.
The moment you add contributions or take withdrawals, simple return becomes misleading. A large contribution near year-end inflates your ending value without being a return on investment. A large withdrawal deflates it. Either way, simple return misattributes the cash flows as investment performance.
Time-Weighted Return (TWR): What Funds Report
Time-weighted return eliminates the distortion of cash flows by breaking the measurement period into sub-periods around each flow, calculating the return for each sub-period, then linking them together. This is the method investment funds use to report performance because it reflects the portfolio manager’s decisions independent of when clients put money in or take it out.
The formula for a two-sub-period example:
TWR = [(1 + R1) × (1 + R2) × …] − 1
where R1, R2 are the returns for each sub-period
You start the year with $50,000. It grows to $55,000 by June (sub-period 1 return = 10%). You add $20,000, making the balance $75,000. By December it grows to $78,750 (sub-period 2 return = 5%).
Simple return: ($78,750 − $50,000) ÷ $50,000 = 57.5% — wildly distorted by the contribution.
TWR: (1.10 × 1.05) − 1 = 15.5% — the actual investment performance.
Money-Weighted Return (MWR / IRR): What You Actually Earned
Money-weighted return (also called Internal Rate of Return, or IRR) tells you something different from TWR: the actual return you earned, accounting for the size and timing of your contributions and withdrawals. Unlike TWR, MWR is affected by when you put money in and take it out.
MWR is the discount rate that makes the net present value of all cash flows equal to zero — essentially the return at which the time value of all your investments and withdrawals balances out to your ending portfolio value. It’s more complex to calculate by hand (it requires iteration) but most brokerage platforms and portfolio tracking apps calculate it automatically.
When is MWR more useful than TWR? When you want to know whether your personal investment decisions — including the timing of your contributions — produced good results. If you happened to make a large contribution right before a market rally, your MWR will be better than TWR. If you contributed heavily before a downturn, it’ll be worse. TWR strips that out; MWR captures it.
Annualizing Returns: Making Different Periods Comparable
A 15% return over 18 months and a 15% return over 3 years are very different things. To compare returns across different time periods, you need to annualize them using CAGR (Compound Annual Growth Rate):
CAGR = (Ending Value ÷ Beginning Value)^(1 ÷ Years) − 1
A portfolio growing from $100,000 to $162,000 over 6 years has a CAGR of:
(162,000 ÷ 100,000)^(1/6) − 1 = 8.35% per year
Our CAGR Calculator does this instantly — enter your beginning value, ending value, and number of years. Use it to compare your portfolio’s annualized return against a benchmark like the S&P 500’s historical average (roughly 10% nominal, 7% real). The CAGR guide explains the concept in more depth, including how it differs from average annual return and why the distinction matters.
Real Return: Adjusting for Inflation
A nominal return of 8% in a year with 4% inflation is a real return of roughly 3.8%. Growing your portfolio’s purchasing power is what actually matters for long-term goals like retirement, so tracking real returns alongside nominal ones gives you a clearer picture. Our guide to nominal vs. real returns covers the full framework, including why a “good” nominal return in a high-inflation environment can still represent a net loss in purchasing power.
Benchmarking: Comparing Your Return to a Standard
Knowing your return is only useful in context. A 9% return sounds great in a year when the market returned 4%, but looks different if the market returned 22%. The most common benchmarks for individual investors:
| Portfolio Type | Appropriate Benchmark |
|---|---|
| US stock-heavy | S&P 500 Total Return Index |
| Total market | Wilshire 5000 or CRSP Total Market |
| International-heavy | MSCI EAFE or MSCI ACWI ex-US |
| Balanced (stocks + bonds) | 60/40 benchmark (60% S&P 500, 40% Bloomberg US Agg) |
| Conservative (bond-heavy) | Bloomberg US Aggregate Bond Index |
The goal of benchmarking isn’t to beat the benchmark every year — most active managers don’t, net of fees, over long periods. The goal is to understand whether your asset allocation and investment choices are producing the returns appropriate for your risk level. If your balanced portfolio consistently underperforms a simple 60/40 index fund, that’s a signal worth examining. Our index fund vs. ETF vs. mutual fund guide covers how passive indexing compares to active management over time.
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