Knowing whether an investment has actually made you money sounds simple, but once you factor in fees, tax, and the difference between total and annualised returns, the picture becomes more complex. Understanding these mechanics helps you compare investments fairly and avoid being misled by headline figures.
This guide walks through how to calculate investment profit properly, from the basic formula to the details that most people overlook.
Gross vs Net Investment Profit
Gross profit is the straightforward calculation: what you sold for minus what you paid.
If you invested 5,000 and sold for 7,200, your gross profit is 2,200.
Net profit is what you actually keep after costs. Those costs include:
- Platform or broker fees (flat fee or percentage per transaction)
- Fund management fees (ongoing charges, expressed as an annual percentage)
- Bid-offer spreads (the difference between the buying and selling price)
- Tax on gains (capital gains tax in the UK and US, which we cover below)
Net profit is the number that actually matters. A 2,200 gross profit can shrink considerably once fees are deducted.
Use the Investment Profit Calculator to enter your buy price, sell price, and fees to see your net return clearly.
How Fees Erode Returns
Fees are one of the most underappreciated factors in long-term investment performance. The reason is compounding: a fee that looks small annually has a large cumulative effect over decades.
Worked example:
You invest 10,000 for 20 years with an average annual return of 7%.
- With no fees: your investment grows to approximately 38,700
- With a 0.25% annual management fee: you end with approximately 36,400
- With a 1.5% annual management fee: you end with approximately 30,700
The difference between a 0.25% and 1.5% fee is around 8,000 over 20 years on a 10,000 investment. That is nearly the entire original investment, lost to fees.
When comparing funds or platforms, always look at the total ongoing charge, sometimes called the ongoing charges figure (OCF) or expense ratio. Low-cost index funds typically charge 0.1-0.25% per year. Actively managed funds often charge 0.75-1.5% or more. The extra cost needs to be justified by outperformance, which most active funds do not consistently deliver.
You can model different return scenarios with the ROI Calculator to see how fee levels affect long-term outcomes.
Capital Gains Tax: UK vs US
Capital gains tax (CGT) applies when you sell an investment for more than you paid. This is not investment advice, and the specifics of your situation should be discussed with a qualified adviser, but here is a brief overview of how it works in each country.
In the UK:
- You have an annual capital gains allowance (the exempt amount). Any gains below this threshold are tax-free.
- Above the threshold, the rate depends on your income tax band. Basic-rate taxpayers pay a lower rate; higher-rate taxpayers pay more. The rates differ for residential property versus other investments.
- ISAs are exempt from CGT entirely, making them a valuable tax-efficient wrapper.
In the US:
- Short-term capital gains (assets held less than one year) are taxed at ordinary income rates, which can be significant.
- Long-term capital gains (assets held more than one year) are taxed at preferential rates: 0%, 15%, or 20% depending on your income level.
- Individual Retirement Accounts (IRAs) and 401(k)s offer tax-advantaged ways to hold investments.
The key practical takeaway from both systems: holding investments for the long term tends to be more tax-efficient than trading frequently, and using tax-advantaged accounts where available reduces your overall tax burden significantly.
Total Return vs Annualised Return
These two figures measure different things and can look very different from each other.
Total return is the percentage gain or loss over the entire holding period. If you invested 10,000 and it is now worth 15,000, your total return is 50%.
Annualised return (sometimes called compound annual growth rate, or CAGR) converts that total return into a per-year figure, accounting for compounding. If that 50% total return was achieved over 8 years, the annualised return is approximately 5.2% per year.
Annualised return is more useful for comparison because it allows you to compare investments held for different lengths of time on a like-for-like basis. A 200% total return sounds excellent, but if it took 30 years, the annualised return is only about 3.5%.
When you see investment fund marketing materials quoting impressive returns, always check whether they are showing total or annualised figures, and over what time period. The same investment can look very different depending on which metric is highlighted.
Dividends as Part of Total Return
Many investors focus entirely on price appreciation and overlook dividends. But for income-generating investments, dividends can represent a substantial portion of total return over time.
If a share price rises from 100p to 115p over a year, the price return is 15%. But if the stock also paid 4p in dividends during that period, the total return is 19% (the 15% price gain plus the 4% dividend yield).
Over long periods, reinvested dividends dramatically increase total return through compounding. Many financial calculators and comparison tools show only price return unless you specifically request total return, which includes dividends. Always clarify which measure you are looking at.
Putting It Together
When evaluating any investment, think through all four components:
- Gross profit - the raw gain before costs
- Net profit - after fees and tax
- Annualised return - so you can compare across different time horizons
- Total return including income - so you do not undercount dividend or interest income
Getting all four right gives you an accurate picture of how an investment has actually performed. Most people only look at the first one.