ROI = ((Returns − Investment) / Investment) × 100. The universal measure of investment performance.
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Use this calculator when preparing for a business decision that depends on this metric. Calculating the figure in advance — rather than estimating — prevents the kind of imprecision that leads to suboptimal choices.
A common mistake is comparing metrics that use different definitions — gross margin versus net margin, revenue versus profit, customer count versus paying customer count. Always confirm the definition of each input before comparing results across periods or sources.
A product manager calculates gross margin for a new product line: manufacturing cost £8.50, proposed retail price £24.99. The calculator returns a 66% gross margin — above the company's 60% threshold, confirming the pricing is viable before taking it to the finance team.
S&P 500 averages ~10%/year. Any investment consistently above this outperforms the market.