Interest calculator

See how much interest your savings or investment earns: simple interest for straightforward calculations, and compound interest with selectable compounding, including a year-by-year growth table.

Simple vs. compound interest

simple: I = P × r × t ÷ 100 · compound: A = P × (1 + r ÷ (100 × m))^(m × t)

With simple interest, interest is always calculated on the original principal, so it is the same every year. With compound interest, accrued interest is added to the principal (compounding), so later periods earn interest on interest — which is why compound interest grows much faster over time.

In the formulas, P is the principal, r the annual rate in percent, t the period in years and m the number of compounding periods per year (1 for annual, 12 for monthly).

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Example

You invest 10,000 KM at 4% per year for 3 years. Simple interest: 10,000 × 4 × 3 ÷ 100 = 1,200 KM. Compound interest with annual compounding: 10,000 × 1.04³ = 11,248.64 KM, i.e. 1,248.64 KM of interest — 48.64 KM more thanks to interest on interest.

What the result means

The calculation is informational and excludes tax on interest income, bank fees and rate changes during the period. For term deposits, banks also publish an effective rate that includes those costs.

Frequently asked questions

What is compounding?

Compounding means adding accrued interest to the principal. The more frequent it is (monthly rather than annually), the higher the final amount, because interest starts earning interest sooner.

When is simple interest used?

Simple interest suits short periods and simple settlements (e.g. late-payment interest). Savings and investments almost always use compound interest in practice.

How does the period affect compound interest?

Exponentially — doubling the period more than doubles the interest. At 4% per year, 10,000 KM grows to 14,802 KM in 10 years but 21,911 KM in 20 years.

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