How to Calculate Your Real Portfolio Return: TWR vs Money-Weighted

Knowing how your investments are performing sounds like it should be the easiest part of investing. You look at your account balance, compare it to what you put in, and you have your return.

But for fundamental, long-horizon investors who make regular contributions or withdrawals, calculating your real portfolio return is rarely that straightforward. If your portfolio is up 10% this year, but you just deposited a large bonus, your brokerage app’s simple percentage might drop overnight—even though the market itself didn't move.

To accurately evaluate your investment decisions, you need to understand the difference between time-weighted return (TWR) and money-weighted return (MWR), why deposits distort basic calculations, and how to find your true performance baseline.

The trouble with simple return formulas

The most basic way to calculate a return is the simple Return on Investment (ROI):

Simple ROI = (Current Value - Total Invested) / Total Invested

If you buy a single block of stock for $10,000 and never touch it again, this formula works perfectly. If the value grows to $12,000, your return is a clear 20%.

But real life is messy. Prudent long-term investors routinely add cash from their paychecks, reinvest dividends, or withdraw funds for major life purchases. Every time cash moves into or out of your portfolio, it mathematically skews the simple return.

Imagine you have a $10,000 portfolio that grows to $20,000 over a few years (a massive 100% gain). Thrilled with this exceptional performance, you deposit an additional $80,000. Your total invested capital is now $90,000, and your overall account value is $100,000. If you look at the simple ROI formula, your overall return suddenly drops to a mere 11% ($100,000 - $90,000) / $90,000. This completely obscures the incredible 100% gain your actual investment decisions generated on your initial capital.

This distortion is why the financial industry relies on two distinct calculation methods to strip out, or properly account for, the noise of cash flows.

Time-weighted return (TWR): Isolating your strategy

Time-weighted return (TWR) measures the compound rate of growth of $1 invested in your portfolio. It deliberately ignores the size and timing of your deposits and withdrawals.

To calculate TWR, you break your investment timeline into smaller "sub-periods." A new sub-period begins every time money enters or leaves the account. You calculate the simple return for each isolated sub-period, and then you link them together geometrically.

For example, if you hold an account for a year but make a deposit in June, you actually have two sub-periods. You calculate the return from January to June (before the deposit), and then the return from June (after the deposit) to December.

The portfolio return formula for linking these sub-periods is:

TWR = [(1 + Return 1) × (1 + Return 2) × ... × (1 + Return N)] - 1

Why is this useful? TWR entirely eliminates the distortion of cash flows, making it the perfect metric to evaluate the quality of your asset allocation or stock picking. When you want to compare your performance against a benchmark like the S&P 500 or a global index, you must use TWR. Market indexes do not have cash flows; they simply track the continuous growth of underlying assets. TWR puts your portfolio on the exact same footing.

Money-weighted return (MWR): Factoring in your cash flows

While TWR measures how well your investments performed, money-weighted return (MWR)—often called the Internal Rate of Return (IRR)—measures how well you performed.

MWR accounts for the size and timing of every single cash flow. It essentially asks: "What single, continuous interest rate would make your starting balance and all your subsequent deposits exactly equal your final portfolio value?"

Because MWR weights the return by the amount of money actually in the account, periods where your account balance is larger will have a heavier impact on the final percentage. If you make a massive deposit right before a market crash, your MWR will suffer heavily, even if your previous small investments did exceptionally well. Conversely, if you drastically increase your investments at a market bottom, your MWR will skyrocket compared to your TWR.

This is arguably the most accurate reflection of the actual wealth generated in your account. The "behavior gap"—the widely documented tendency for average investors to underperform simple index benchmarks—is heavily visible in the space between an investor's TWR (what their assets did) and their MWR (what the investor actually took home due to the timing of their trades).

A concrete example of TWR vs MWR

Let’s walk through a simplified, two-year scenario to see how these investment return calculation methods diverge in practice.

The setup:

• Year 1 start: You invest $10,000.
• Year 1 end: The market has a great year. Your portfolio grows to $12,000.
• Action: Excited by the 20% gain, you deposit an additional $5,000 at the very end of Year 1. Your new balance is $17,000.
• Year 2 end: The market experiences a minor correction. Your portfolio drops 10%, leaving you with $15,300.

Calculating simple ROI: You invested a total of $15,000 ($10,000 initial + $5,000 deposit). You ended with $15,300. ($15,300 - $15,000) / $15,000 = 2.0% The simple return says you made 2.0% overall.

Calculating time-weighted return (TWR): We isolate the two periods, completely ignoring the absolute dollar amounts and focusing only on the percentage growth of the assets.

• Period 1 Return: +20% (0.20)
• Period 2 Return: -10% (-0.10)
• TWR = [(1 + 0.20) × (1 - 0.10)] - 1
• TWR = [1.20 × 0.90] - 1 = 0.08 The assets themselves generated an 8.0% return over the two years. If you were comparing your performance to an index fund that held the same assets, the benchmark to beat is 8.0%.

Calculating money-weighted return (MWR): Using an IRR equation (which requires trial-and-error algebra or spreadsheet software), we find the single annualized rate that turns your $10,000 initial investment and your $5,000 Year 1 deposit into exactly $15,300 at the end of Year 2. The MWR comes out to approximately 1.19% annualized.

The takeaway: Your TWR is 8.0%, but your MWR is less than 2% per year. Why? Because your portfolio manager (you) picked assets that did relatively well over two years. But your personal cash flow timing worked against you. You only had $10,000 invested during the 20% boom, but you had $17,000 exposed to the 10% drop. Your MWR reflects the reality of having heavier exposure during the downturn.

The multi-currency complication

If you hold international investments, calculating your real return gains another layer of complexity: foreign exchange (FX) rates.

Imagine an investor based in the United Kingdom who buys a U.S. stock. Over the course of the year, the U.S. stock climbs by 10% in U.S. Dollars (USD). However, during that same year, the USD weakens by 5% against the British Pound (GBP).

If the investor logs into a U.S. brokerage account, their return looks like a flat 10%. But their purchasing power in their home country has not increased by 10%. When those USD assets are translated back to GBP, the true portfolio return is roughly 5%.

To find your real return, you must always evaluate your portfolio in your base currency. This means calculating the start values, cash flows, and end values converted at the exchange rates active on those specific historical dates. Failing to account for currency drag can create the illusion of strong performance while your local purchasing power remains essentially flat.

Which metric should you actually use?

The short answer is that fundamental investors should track both. They answer fundamentally different questions about your financial health.

Use Time-Weighted Return (TWR) to grade your strategy. If you are picking individual stocks, selecting actively managed mutual funds, or building a custom asset allocation, you need to know if your choices are actually beating a simple, low-cost index fund. TWR allows you to compare your portfolio apples-to-apples against the broader market.

Use Money-Weighted Return (MWR) to grade your wealth creation. This is the ultimate reality check. It tells you exactly how fast your actual dollars are growing, factoring in your real-life savings habits and timing. If your MWR consistently lags your TWR, it may be a sign that you are unwittingly chasing performance—investing heavily after markets have already run up, and pulling back during downturns.

Ultimately, understanding how to calculate portfolio return properly strips away the noise of deposits, withdrawals, and currency fluctuations. By keeping an eye on both your TWR and MWR, you maintain a clear, objective view of your progress, allowing you to make practical, data-driven decisions for your long-term financial future.