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Compound Interest Calculator

UK Savings Calculator

See how your money grows with compound interest. Calculate savings for ISAs, savings accounts, or any regular deposits over time.

Your Savings Plan

Enter your savings details to see how your money grows

£
£

Your Savings Growth

See how your savings will grow over time

£32,703
Total after 10 years
Total Contributions
£25,000
Interest Earned
£7,703
Interest Bonus

You'll earn £7,703 in interest, which is 30.8% on top of your contributions.

Initial deposit£1,000
Monthly contributions (10 years)£24,000
Total interest earned£7,703
Effective annual rate (APY)5.12%
Final balance£32,703
Monthly Breakdown
Monthly contribution
£200
Avg. monthly interest
+£64

Monthly Savings Examples

Monthly Savings5 Years10 Years20 YearsCalculator
£100/month6,78015,48039,600Calculate →
£200/month13,56030,96079,200Calculate →
£300/month20,34046,440118,800Calculate →
£500/month33,90077,400198,000Calculate →
£1000/month67,800154,800396,000Calculate →

*Estimates based on 5% annual interest rate, compounded monthly. Actual results vary.

Understanding Compound Interest

Compound interest is often called the eighth wonder of the world. Unlike simple interest which only calculates on your original deposit, compound interest earns interest on your interest, creating exponential growth over time.

The Power of Starting Early

Time is the most important factor in compound growth. Someone who saves £200/month from age 25 to 35 (10 years, £24,000 total) and then stops, will often have more at 65 than someone who starts at 35 and saves until 65 (30 years, £72,000 total), thanks to the extra years of compounding.

Compound Frequency Matters

Interest can compound daily, monthly, quarterly, or annually. More frequent compounding means slightly higher returns. A 5% rate compounded daily gives an effective annual rate (APY) of about 5.13%, while annual compounding stays at exactly 5%.

Tax-Free Savings with ISAs

In the UK, you can save up to £20,000 per year in an Individual Savings Account (ISA) and pay no tax on the interest earned. This makes ISAs ideal for long-term savings as all your compound growth remains tax-free.

Frequently Asked Questions

How does compound interest work?

Compound interest means you earn interest on both your original deposit and on previously earned interest. For example, if you deposit £1,000 at 5% annual interest, after year one you have £1,050. In year two, you earn 5% on £1,050 (not just £1,000), giving you £1,102.50. This compounding effect accelerates your savings growth over time.

How much should I save each month?

A common guideline is to save at least 20% of your income, following the 50/30/20 rule (50% needs, 30% wants, 20% savings). However, any amount is better than nothing. Start with what you can afford and increase gradually. Even £50-£100 per month can grow significantly over 10-20 years with compound interest.

What is the best savings account interest rate in the UK?

Savings rates vary by account type. Easy access accounts typically offer 4-5% (as of 2025). Fixed-rate bonds may offer higher rates for locking money away. Cash ISAs provide tax-free interest up to your £20,000 annual allowance. Always compare current rates as they change frequently.

Is it better to save monthly or as a lump sum?

If you have a lump sum available, investing it immediately typically performs better due to more time for compound interest. However, regular monthly savings (pound-cost averaging) is more practical for most people and builds good habits. Our calculator shows results for both initial deposits and monthly contributions.

How much will £200 a month grow to in 10 years?

Saving £200 per month for 10 years at 5% interest would give you approximately £31,000. Your total contributions would be £24,000, meaning you earn about £7,000 in compound interest. Use our calculator above to see exact figures for your situation.