Finance

Investment Simple Interest Total Calculator (30 Years)

Calculate simple interest and the total amount to repay. This investment version uses a 30-year planning term as its starting point.

The Interest figure is the extra cost of borrowing over 30 years, and the Total figure is the original amount plus that interest, so the full amount to repay is the Total, not just the amount borrowed.

Formula

Simple interest equals principal times rate times time, divided by 100.

How it works

Interest is charged only on the original principal, not on interest already added.

Worked example

Principal $10,000, annual rate 5%, term 30 years. Using the page formula, simple interest equals $10,000 times 5 times 30, divided by 100, which is $15,000.00. Total to repay is $10,000 plus $15,000.00, which is $25,000.00. That is the calculator's own output for these defaults.

Because simple interest never compounds, the interest grows by the same $500 every year: after 30 years it is 30 times $500, which is $15,000.00. At 30 years the interest is one and a half times the amount borrowed, which is why a mortgage-length simple-interest loan should never be judged on its yearly interest alone.

Who this term suits for an investor: an investor comparing a loan as long as a typical mortgage, who must check what happens if rental income or business income falls for several years, because a 30-year simple-interest bill does not shrink when income does.

FAQs

What is simple interest?
Simple interest is interest charged only on the original amount, not on accumulated interest.

Is this investment calculator exact?
No, it is an estimate for planning only, based on the numbers you enter.

Are these figures financial advice?
No, they are estimates for planning only, not financial advice. Check with a qualified adviser for decisions involving large sums.

Is a 30-year investment loan the same as a 30-year mortgage?
Not usually: a mortgage is normally repaid in monthly instalments and its interest compounds on the falling balance, while this page charges simple interest on the full $10,000 for all 30 years.

Why does the interest reach $15,000 after 30 years?
Because 30 years at $500 a year is $15,000, one and a half times the amount borrowed, which is the price of stretching a simple-interest loan to mortgage length.

What happens if rental income falls during a 30-year plan?
The interest bill does not fall with it, so the investor must have reserves or another income source, or the loan can quickly become unaffordable.

Estimates only, not financial advice. Figures are approximate and do not include all fees, taxes, or changing rates unless stated.