Savings & investing
Premium Bonds probability calculator
Premium Bonds don't pay interest — you enter a monthly prize draw instead. Enter your holding to see the actual probability of winning each month, your expected return at the current NS&I prize-fund rate, and how it compares with a normal easy-access savings account.
- Expected return (mean, per year)
- £380
- Chance of any prize this month
- 36.5%
- Chance of any prize in 12 months
- 99.6%
| Number of £1 bonds | 10,000 |
|---|---|
| Expected prizes per yearMean number of wins at these odds | 5.45 |
| Chance of any prize over 5 years | 100.0% |
| If held in easy-access savings at 4.00%Guaranteed interest, taxable; uses your Personal Savings Allowance | £400 |
| If held in easy-access savings at 4.50%For comparison only | £450 |
The “expected return” is a mathematical mean — actual returns are highly skewed by rare large prizes. Most holders, especially with small balances, win less than the headline rate. The median return for a £1,000 holding is typically £0 in a year. Prize-fund rate and odds are set by NS&I and change from time to time; the defaults reflect the most recent confirmed draw — check nsandi.com for the current figures.
How it works
- Every £1 bond has the same odds of winning in each monthly draw — currently 22,000 to 1. The probability of at least one prize from N bonds in one draw is 1 − (1 − 1/22,000)^N.
- Over a year that is 12 independent draws, so the chance of any prize in 12 months is 1 − (1 − 1/22,000)^(12N). We extend the same maths to 5 years (60 draws).
- The 'expected return' multiplies your holding by NS&I's annual prize-fund rate. That is the mathematical mean across all bondholders — because the prize pool includes two £1 million jackpots, most individual holders win less than the headline rate.
Common questions
- What are the current Premium Bonds odds?
- NS&I sets the odds per £1 bond per monthly draw. The most recent published odds are 22,000 to 1 with a prize-fund rate of around 3.80%. NS&I can change both at any time — always check nsandi.com for the live figures before relying on a calculation.
- Why is my expected return lower than the prize-fund rate suggests?
- The prize-fund rate is the mean across all bondholders, but the prize pool includes two £1 million jackpots and many large prizes. Most ordinary holders never win those, so the median return is well below the mean — often £0 in any given year on a small holding.
- Are Premium Bonds better than a savings account?
- If you pay tax on savings interest and have already used your Personal Savings Allowance, the tax-free nature of Premium Bonds prizes makes them competitive — but only as a like-for-like comparison with the headline prize-fund rate, not your typical return. For guaranteed interest, a cash ISA or fixed-rate savings account is usually more predictable.
- Are Premium Bonds safe?
- Your capital is 100% backed by HM Treasury, so you can cash out any time at face value. They are not covered by the FSCS, but the Treasury backing is regarded as equivalent. The risk is not losing your money — it is winning less than inflation.