Simple vs Compound Interest: Key Differences
Compare linear simple interest and compound growth with side-by-side numbers, formulas and practical use cases.
Simple vs Compound Interest: Key Differences
Compare linear simple interest and compound growth with side-by-side numbers, formulas and practical use cases. Use the free RapidCalc calculator to check your own numbers and explore different inputs.
What differs between them
Simple interest pays on the original principal. Compound interest pays on principal plus interest credited in earlier periods. With a positive rate, compound growth generally pulls ahead over time.
Side-by-side example
Starting with $10,000 at 5% annually for three years: simple interest yields $11,500. Annual compounding gives $10,000 × 1.05³ = $11,576.25, a difference of $76.25.
Compounding frequency
For nominal annual rate r compounded n times per year, future value = P × (1 + r/n)^(n×t). This guide compares annual compounding unless stated otherwise.
Why time matters
The difference is often modest in a short interval but grows over longer horizons. On debt, compounding can increase costs; on savings, it can increase accumulated value.
Compare like with like
Be careful when comparing advertised rates. Effective annual yield and nominal APR may use different compounding assumptions, and taxes or fees can materially change net results.
Try your own example
Open the interactive calculator and change one number at a time to see the effect. Read the assumptions attached to the result before applying it to a real transaction.
Related tools
Educational information only; product rules, tax rates and financial terms vary.