Learning goals
- Calculate ROI from gain (or net profit) and cost
- Decide which costs and proceeds belong in the ROI inputs
- Recognize when a simple ROI needs time-adjusted or annualized context
What ROI measures
Return on investment (ROI) asks: for each dollar you put in, how much net return did you get? A 25% ROI means you gained $0.25 of net profit per $1.00 of cost (or you recovered cost plus 25%).
ROI is popular because it is easy to communicate. It is also easy to misuse: leave out fees, ignore time, or compare a 3-month project to a 3-year project as if the percents were interchangeable.
Before you calculate, write down what “cost” includes (purchase price, fees, ads, materials) and what “gain” or “final value” includes (sale proceeds, revenue, residual value). Consistent definitions matter more than decimal precision.
Basic ROI
ROI = ((final value − cost) ÷ cost) × 100
Equivalently ROI = (net profit ÷ cost) × 100 when net profit = final value − cost. A negative ROI means you lost money relative to cost.
ROI from explicit gain
ROI = (net gain ÷ investment cost) × 100
Use this when gain is already computed (for example, profit after expenses). Do not forget to subtract the original investment if your “gain” figure still includes returned principal.
Example 1 — Simple investment ROI
Given
You buy shares for $1,000.00 and later sell them for $1,250.00. Ignore fees. What is ROI?
Steps
- Cost = $1,000.00; final value = $1,250.00.
- Net profit = 1,250 − 1,000 = $250.00.
- ROI = (250 ÷ 1,000) × 100 = 25%.
Answer
ROI is 25%.
Tip: If trading fees were $20.00 round-trip, cost basis effectively rises and ROI falls — include fees when they matter.
Example 2 — Marketing campaign
Given
An ad campaign costs $800.00 and produces $2,000.00 of attributable profit (after product costs, before the ad spend).
Steps
- Clarify net gain after ads: profit after product costs is $2,000.00 then subtract ad cost $800.00 → net $1,200.00.
- ROI = (1,200 ÷ 800) × 100 = 150%.
- If someone naively divides $2,000.00 by $800.00 without subtracting ads, they double-count.
Answer
Campaign ROI is 150% on the ad spend (with the profit definition above).
Tip: State whether revenue or profit sits in the numerator — they are not the same.
Example 3 — Same ROI, different timelines
Given
Project A returns 20% in 3 months. Project B returns 20% in 2 years. Are they equal?
Steps
- Simple ROI is 20% for both if net profit ÷ cost = 0.20.
- Per year, A is much stronger: rough annualization is higher for the short project.
- Simple ROI alone does not rank them; add time (or use annualized return / CAGR) when horizons differ.
Answer
Equal ROI percents are not equal opportunities unless the time spans match.
Tip: For multi-year growth, compound-interest style annualization is usually clearer than raw ROI.
Leaving costs out of the denominator
Common mistake
Buy for $1,000.00 pay $50.00 fees, sell for $1,200.00 → ROI = 200/1,000 = 20% and ignore fees.
Better approach
Treat total invested capital as $1,050.00 (or subtract fees from proceeds consistently). Net = 1,200 − 1,050 = $150.00 → ROI ≈ 14.3%.
Check your understanding
1.Cost $400.00 sell for $460.00. ROI?
Answer: ((460 − 400) ÷ 400) × 100 = 15%.
2.Invest $2,000.00 end with $1,700.00. ROI?
Answer: ((1,700 − 2,000) ÷ 2,000) × 100 = −15%.
3.Profit $300.00 on a $1,200.00 project cost. ROI?
Answer: (300 ÷ 1,200) × 100 = 25%.
4.Why compare ROI only among similar timeframes?
Answer: ROI ignores how long capital was tied up unless you annualize.
Key takeaways
- ROI = ((final value − cost) ÷ cost) × 100, or net gain ÷ cost × 100.
- Define cost and gain the same way every time — include material fees.
- Negative ROI means a loss relative to what you invested.
- When time spans differ, supplement simple ROI with an annualized measure.