What Is ROI? (And Why the Same Idea Looks Different in Each Box)

Learning Objectives

By the end of this lesson, you should be able to:

• Calculate a basic ROI given a gain and a cost.
• Explain what ROI is actually measuring.
• Recognize ROI as a cross-box concept, and identify one limitation.

Core Content

The ROI Formula

ROI = (Gain from Investment − Cost of Investment) ÷ Cost of Investment, usually expressed as a percentage. If $1,000 grows to $1,200, the gain is $200, and ROI = $200 ÷ $1,000 = 20%.

The Same Concept, Different Boxes

ROI isn't a WHITE-box-only idea. A RED-box real estate investor calculates ROI on rental income and appreciation against purchase price. A BLUE-box business owner calculates it on profit generated against money invested. The formula's logic stays the same — gain compared to cost — but what counts as gain and cost changes by box.

A Real Limitation

Basic ROI doesn't account for time. A 20% ROI earned in one year is very different from the same 20% earned over ten years, even though the formula alone doesn't show that difference.

Worked Example

$500 growing to $575 is a $75 gain: ROI = $75 ÷ $500 = 15%. A $10,000 business equipment purchase generating $2,500 in extra profit: ROI = $2,500 ÷ $10,000 = 25% — same formula, very different situations.

Practice Quiz

1. ROI measures:

1. True or False: Basic ROI accounts for how long it took to earn the

1. You invest $2,000 and it grows to $2,400. What is the ROI?

Answer Key

1. B
2. False
3. C

Answers and Explanations

Question 1

Correct answer: B. ROI is specifically a percentage measure of gain relative to cost.

Question 2

Correct answer: False. Basic ROI does not factor in time — a real limitation.

Question 3

Correct answer: C. ($2,400 − $2,000) ÷ $2,000 = 20%.

Key Takeaways

• ROI = (Gain − Cost) ÷ Cost, usually expressed as a percentage.
• ROI applies across real estate, business, and paper assets alike.
• Basic ROI doesn't account for time — a real limitation to keep in