Savings Interest Calculator

How to Use This Calculator

Enter an initial deposit, a regular contribution amount and how often you'll make it (monthly, quarterly, or annually), the annual interest rate, and the number of years. The calculator models compound interest — meaning interest earned is added to your balance and also earns interest in future periods.

The chart and year-by-year table make it easy to see how your savings grow over time and how much of the final balance comes from your own deposits vs interest. The gap between the two widens considerably over longer time horizons, demonstrating the power of compounding.

Common Use Cases

• Emergency fund planning: Find how long it takes to build a 3–6 month expense buffer
• Savings goals: See when you'll reach a target amount for a house deposit, car, or holiday
• ISA projections: Model growth in a cash ISA or stocks & shares ISA at different interest rates
• Interest rate comparison: Compare two savings accounts side-by-side by entering different rates
• Children's savings: Project a Junior ISA or savings account started at birth
• Lump sum vs regular deposits: Compare putting a windfall to work vs steady monthly saving

Tips & Tricks

Monthly beats annual: Depositing monthly rather than annually results in slightly more interest because your money is invested for longer during the year. The difference compounds significantly over decades.

Start early: Thanks to compounding, £100/month started at 25 grows far more than £200/month started at 45. Try comparing the two in this calculator — the results are striking.

Inflation: This calculator shows nominal growth (before inflation). Real purchasing power depends on the interest rate exceeding inflation. If your account pays 4.5% and inflation is 3%, your real return is roughly 1.5% per year.