ROI Guide

Quick answer

ROI measures how much return you get compared with how much you invested. If you invest £1,000 and make £200 net profit, ROI is 20%. ROI is useful, but it should not be judged without time, risk, effort, and cash flow.

ROI formula

ROI = Net return ÷ Investment cost × 100

Time changes ROI

A 20% ROI in one month is very different from 20% over five years. ROI does not automatically show speed. For longer comparisons, annualised return may be more useful. Always ask: how long did the money take to produce that return?

Risk and effort

Two projects can have the same ROI but very different risk. One may be stable and passive; another may depend on constant work, stock risk, ad spend, or market timing. A good ROI decision considers the quality of the return, not just the percentage.

Marketing ROI

In marketing, ROI can be hard to measure because not every sale is tracked perfectly. Some campaigns build awareness before conversion. For paid ads, combine ROI with ROAS, customer acquisition cost, profit margin, and lifetime value.

Common mistakes

• Ignoring time period.
• Using revenue instead of net profit.
• Forgetting fees and labour.
• Comparing high-risk and low-risk returns as equal.
• Ignoring cash flow timing.
• Treating projected ROI as guaranteed.

Practical takeaway

Use ROI as a first filter, then add context. Ask whether the return is repeatable, how long it takes, what risk is involved, and what else the money could do. The best ROI is not always the highest number; it is the best risk-adjusted use of resources.