Practical guide

How to Calculate ROI

Calculate return on investment and avoid common interpretation mistakes.

Quick Answer

ROI = (net gain ÷ cost of investment) × 100, where net gain is final value minus initial cost. To compare investments held for different lengths of time, annualise it: annualised ROI = [(final ÷ initial)^(1÷years) − 1] × 100.

Step-by-Step Method

Total the full cost of the investment, including fees, setup, and any ongoing costs — not just the headline purchase price.
Determine the final value or total return received.
Subtract cost from final value to get net gain, divide by cost, and multiply by 100.
If the holding period is not one year, annualise the result so it can be compared with other opportunities.

Worked Example

You invest $12,000 and the position is worth $15,600 three years later. Net gain = $3,600, so simple ROI = 3,600 ÷ 12,000 × 100 = 30%. Annualised, that is (15,600 ÷ 12,000)^(1/3) − 1 = 9.1% per year — a very different figure from 30%, and the one you should use when comparing against a one-year alternative.

Detailed Explanation

The single most common ROI error is comparing returns across different time horizons without annualising. A 30% return sounds strong until you learn it took three years, at which point it is 9.1% annually — respectable, but no longer obviously better than a shorter investment returning 12% in a year. Any time you see an ROI quoted without a period attached, the number is close to meaningless.

The second common error is an incomplete cost base. ROI is only as honest as its denominator, and it is tempting to count the purchase price while quietly omitting transaction fees, maintenance, taxes, or the cost of capital. For a marketing campaign this means including staff time, not just ad spend; for a property it means closing costs, repairs, and vacancy months.

ROI also ignores risk entirely, which is its deepest limitation. A 15% return from government bonds and a 15% return from a speculative venture are identical in ROI terms and completely different as decisions. It says nothing about the chance the investment could have gone to zero. Use ROI to measure what happened, and use judgement about volatility and downside to decide what to do next.

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FAQ

What counts as a good ROI?

It depends entirely on risk and alternatives. The usual benchmark is what you could earn passively — a broad stock index has historically returned roughly 7–10% annually. An investment should beat that meaningfully to justify extra risk or effort.

What is the difference between ROI and ROAS?

ROAS (return on ad spend) divides revenue by advertising cost only. ROI divides profit by total cost. ROAS can look strong while ROI is negative, because ROAS ignores cost of goods, labour, and overhead.

Can ROI be negative?

Yes. If final value is below total cost, net gain is negative and so is ROI. An ROI of −100% means the entire investment was lost.