Premium Bonds Calculator

The Premium Bonds Calculator helps UK savers see how their NS&I Premium Bonds might grow, how long it could take to reach the £50,000 maximum, and what their real odds of winning prizes are each month.

By combining your balance, monthly contributions, and the current prize fund rate, you’ll get a realistic view of your potential returns — all tax-free.

How to Use the Premium Bonds Calculator

Step 1: Enter your initial amount
Start by entering how much you already hold in Premium Bonds (up to the NS&I limit of £50,000).
Example: If you currently hold £10,000, type 10000.

Step 2: Add your monthly contributions
Next, input how much you plan to add each month.
The calculator will show how quickly your balance grows and when you’ll reach the £50,000 cap.
Once your total hits the maximum, the tool automatically stops adding new contributions.

Step 3: Choose whether to reinvest your winnings
Tick the box to reinvest prizes into more Premium Bonds, or leave it unticked to take prizes as cash.
Reinvesting helps your balance grow faster, although it still stops at the £50,000 cap.

Step 4: Adjust the prize rate
By default, the calculator uses the current NS&I prize fund rate (3.6%).
This rate changes from time to time, so you can update it if NS&I adjusts their figures.
The Premium Bonds Calculator is refreshed monthly, but you can change the percentage manually any time.

Step 5: Review your projections
Once you’ve entered your details, the interactive chart shows:

• How your Premium Bonds balance grows over time.
• When you’ll reach the £50,000 maximum.
• Your expected winnings and projected total balance.

Hover over the line to see estimated values at different points in time.

Step 6: Understand your prize odds
The calculator includes an odds and prize probability section that estimates:

• Your chance of winning any prize each month or year.
• The expected number of prizes you might win.
• The probability of winning 0, 1, or multiple prizes in a given month.

You can also explore:

• What are the odds of winning Premium Bonds?
• How long could it take to win the Premium Bonds jackpot?
• Premium Bonds vs Savings Accounts – Which Is Better in 2025?

Why Use a Premium Bonds Calculator?

• See realistic growth based on your balance, reinvestment, and prize rate.
• Understand your odds using NS&I’s official probability figures.
• Compare Premium Bonds to ISAs or savings accounts to see if they’re right for you.
• Visualise progress toward the £50,000 limit and your long-term prize potential.

This makes the calculator especially useful for UK savers deciding between Premium Bonds, Cash ISAs, and fixed-rate savings accounts.

Example: Building Up to £50,000

Let’s say you start with £10,000 and add £250 each month while reinvesting all winnings.

• You’d reach £50,000 in roughly 13 years.
• At a 3.6% prize rate, your expected annual return could be around £1,400 (though it varies randomly).
• Because Premium Bonds are tax-free, that’s equivalent to earning a higher interest rate in a taxable account if you’re a higher-rate taxpayer.

Are Premium Bonds a Good Idea?

Premium Bonds can be a smart choice if you:

• Want capital safety (your money is fully backed by HM Treasury).
• Prefer tax-free returns.
• Enjoy the small chance of winning big prizes.

However, if you want guaranteed returns or are saving for short-term goals, a Cash ISA or high-interest savings account may be better.

For more on this, see:

• Are Premium Bonds Worth It in 2025?
• Premium Bonds vs Stocks & Shares ISA – Which Makes More Sense?

Frequently Asked Questions – Premium Bonds Calculator

How does the Premium Bonds Calculator work?
It projects your balance growth and potential returns based on your investment, monthly additions, reinvestment choice, and NS&I’s current prize fund rate.

Can the calculator predict jackpot wins?
No — jackpot wins are completely random. The calculator only estimates probabilities based on how many bonds you hold.

What’s the maximum I can hold in Premium Bonds?
You can hold up to £50,000 per person. Once you reach this amount, no more contributions can be made.

Do Premium Bonds always return 3.6%?
No — 3.6% is an average “prize fund rate.” Some people earn more, some less, and some nothing. The rate may also change over time.

Are Premium Bonds tax-free?
Yes. All Premium Bonds prizes are 100% tax-free, making them particularly attractive for higher-rate taxpayers.

Should I reinvest or take winnings as cash?
If your goal is to maximise your balance and win chances, reinvest. If you prefer regular income, choose cash payouts.

Can I lose money with Premium Bonds?
No. Your capital is safe with NS&I. The only “risk” is that you might earn less than with traditional savings.

How accurate is the calculator?
It uses NS&I’s official odds and distributions for a realistic view, but because prizes are random, actual results will differ.

Compare with Other Tools

You can also explore:

• Investment Calculator – for compound interest and ISA projections.
• Inflation Calculator – to see the real value of your money over time.
• Retirement Calculator – for long-term planning.

Disclaimer

The Premium Bonds Calculator is an educational tool designed to help you understand how Premium Bonds work and estimate potential returns. It does not predict future winnings or guarantee performance. All figures are based on current NS&I data and average prize rates. Consider your own financial goals or seek regulated advice before investing.ize odds based on current NS&I rates