Money Math · Percentages · Lesson Plan
Calculating Interest — Worksheets and Lesson Plan for Teachers
A lesson and printable worksheets on calculating interest using the formula I = P × R × T — practice applying percentages to money in real-world borrowing and saving scenarios. The classic lesson page is free to read; the matching printable worksheets are available with Full Membership.
What Students Learn
Learning objectives
- Key vocabulary: principal (the starting amount), rate (the percentage per year), and time period
- The interest formula: I = P × R × T — and how to plug in values to find an interest amount
- How to calculate interest earned on a savings amount given a principal, rate, and time
- How to calculate interest owed on a borrowed amount — and how the same formula applies to both savings and loans
- How to interpret the result: what the interest dollar amount means relative to the principal
For Teachers
How to use this lesson
This lesson focuses on the mechanics of the interest formula — plugging in values, doing the arithmetic, and interpreting the result. It is worksheet and practice-problem oriented, making it a good follow-up to a conceptual lesson on what interest is and why it matters.
Best used after students have been introduced to the concept of interest — what it is, why it exists, and how it affects saving and borrowing. The banking section has free conceptual lessons on simple and compound interest that make a strong pair with this practice resource.
Works well in math class as a percentages application unit, or in a financial literacy class as reinforcement for a banking or credit lesson. Grades 6–9; adaptable for remediation in Grades 10–11.
Related Banking Lessons
Looking for the conceptual lessons — what interest is, how it works in savings accounts and loans, and how simple interest differs from compound interest? Those are in the Banking section:
What Is Simple Interest? — free lesson + video (Grades 6–12)
What Is Compound Interest? — free lesson + video (Grades 7–12)
This page is the calculation practice resource — use it after the banking concept lessons to give students formula drill and worksheet practice.
Legacy Resource
Calculating Interest Lesson Plan
The classic lesson — covering principal, rate, time, and the I = P × R × T formula — is free to read. Printable worksheets and classroom activities are available with Full Membership.
This is a legacy resource from the classic MoneyInstructor library. The lesson page is free to read. Printable worksheets require Full Membership through the existing member system.
Related Resources
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