Interest & Compound Interest Calculator
Enter starting capital, rate, term and an optional monthly deposit to see final balance, total paid in and interest, with yearly or monthly compounding.
Interest is credited once a year and earns interest from then on. The contribution is paid in at the end of each month and earns pro-rata interest in the current year.
Final capital
€16,288.95
Total deposits
€10,000.00
Interest earned
€6,288.95
| Year | Balance | Deposits | Interest |
|---|---|---|---|
| 1 | €10,500.00 | €10,000.00 | €500.00 |
| 2 | €11,025.00 | €10,000.00 | €1,025.00 |
| 3 | €11,576.25 | €10,000.00 | €1,576.25 |
| 4 | €12,155.06 | €10,000.00 | €2,155.06 |
| 5 | €12,762.82 | €10,000.00 | €2,762.82 |
| 6 | €13,400.96 | €10,000.00 | €3,400.96 |
| 7 | €14,071.00 | €10,000.00 | €4,071.00 |
| 8 | €14,774.55 | €10,000.00 | €4,774.55 |
| 9 | €15,513.28 | €10,000.00 | €5,513.28 |
| 10 | €16,288.95 | €10,000.00 | €6,288.95 |
Note: These calculations are for informational purposes only and do not replace professional tax or financial advice. All information without guarantee.
FAQ
Frequently Asked Questions
What is the compound interest effect?
With compound interest, returns are reinvested and earn interest themselves. Capital grows exponentially. At 5 % p.a. money doubles in approx. 14.4 years (Rule of 72: 72 ÷ rate).
What are good savings rates in Germany in 2026?
According to ECB interest rate statistics, the average rate on overnight deposits of German households was 0.5 % in August 2026 (including current accounts); new fixed deposits up to 1 year averaged about 2.3 %, over 2 years about 2.7 %. Individual overnight and fixed-deposit offers are clearly higher – comparing is worthwhile.
How do I calculate the real interest rate?
Real rate ≈ nominal rate − inflation rate. At 3 % nominal and 2.2 % inflation (2025 average) the real rate is only approx. 0.8 %. That is the actual purchasing power gain of your savings.
What does p.a. mean?
"p.a." stands for "per annum" (Latin: per year). A rate of 4 % p.a. means 4 % interest per year. Monthly: 4 % ÷ 12 ≈ 0.333 % per month.
Guide
What is the Interest & Compound Interest Calculator?
The interest calculator computes interest, compound interest and final capital for savings and investments. It supports simple and compound interest as well as regular contributions.
How does the Interest & Compound Interest Calculator work?
Enter starting capital, interest rate, term and optional monthly savings. Simple interest: interest = capital × rate × years. Compound interest: final capital = capital × (1 + rate)^years. With monthly contributions the geometric series is used.
Key Data and Facts
Compound interest: at 5 % p.a. capital doubles in approx. 14.4 years (Rule of 72: 72 ÷ rate). Deposit rates Germany (ECB, 08/2026): overnight deposits average 0.5 % (including current accounts), new fixed deposits up to 1 year approx. 2.3 % p.a. Inflation (Destatis): 2025 average 2.2 %, September 2026 3.3 % (provisional). Real return = nominal rate minus inflation.
Step-by-Step Guide
Step-by-step: 1. Enter capital and rate. 2. Choose the interest method: compound with annual or monthly crediting, or simple interest without compounding. 3. Set term in years. 4. Optional monthly savings. 5. Read final capital. 6. Rule of 72: years to double = 72 ÷ rate (%)
Calculation Example
5,000 EUR, 3 % p.a., 10 years compound: final capital 6,720 EUR, interest 1,720 EUR (simple interest: 1,500 EUR). With 100 EUR/month paid at the end of each month and annual crediting: final capital 20,665 EUR, of which 17,000 EUR deposits (5,000 + 12,000) and 3,665 EUR interest. With monthly crediting: 20,721 EUR.
Sources
Official sources
Calculations are based on applicable German laws and official data:
- Deutsche Bundesbank
- Bundesanstalt für Finanzdienstleistungsaufsicht (BaFin)
- Statistisches Bundesamt (Destatis)
Full methodology at Methodology.
Reviewed by Konstantin Iakovlev · Last updated:
Finance
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