Interest I = P × (r/100) × t. Total = P + I. Time t is in years (or same unit as rate).

Use time in years (e.g. 6 months = 0.5) or use an annual rate and time in years.

Simple interest is only on the principal. Compound interest is on principal plus prior interest.

Online Simple Interest Plus Principal Calculator

Calculate simple interest and total (interest + principal). P, r, t.

Principal (P)

Rate (% per year)

Time (years)

Frequently Asked Questions

What is the formula?: Interest I = P × (r/100) × t. Total = P + I. Time t is in years (or same unit as rate).
How do I use months?: Use time in years (e.g. 6 months = 0.5) or use an annual rate and time in years.
Simple vs compound?: Simple interest is only on the principal. Compound interest is on principal plus prior interest.

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