Premium Bonds calculator
The million is real. So is what it costs you.
Premium Bonds are capital-safe, tax-free and genuinely fun. At average luck they are also a little behind a plain savings account. This works out by exactly how much, and shows you the odds without flattering them.
Your Bonds
£25 minimum, £50,000 maximum - that ceiling is NS&I’s, not ours.
The best easy-access rate with no balance cap and no introductory bonus, so it is a rate you could put the whole holding into.
What the dream costs you
That is the gap after 5 years, at exactly average luck: £6,169 in a 4.21% savings account against £6,044 in Bonds. Your £5,000 is never at risk in either. What you are spending is the difference.
Over 5 years, £5,000 in Premium Bonds at average luck reaches £6,044, against £6,169 in a 4.21 percent savings account. The gap is £125. Expected winnings at average luck are £190 a year. The chance of winning nothing at all next year is 6.5%. The odds of a one million pound prize this year are 1 in 1,140,000.“Average luck” is doing a lot of work in that sentence. The three numbers below are what it actually looks like.
What average luck actually looks like.
Expected winnings a year
£190
At exactly average luck
The prize fund pays out 3.80% of everything held, spread across six million prizes a month. It is a share-out figure, not a prize anyone is handed.
Chance of winning nothing
6.5%
Across all twelve draws next year
Twelve draws, £5,000 of Bonds, not a single prize. Straight from NS&I’s published odds of 1 in 22,000 per £1 Bond.
Odds of the £1m this year
About 1 in 1,140,000
Two jackpots, every month
2 jackpots a draw, drawn from 137 billion eligible £1 Bonds. Somebody wins it. Twice a month, somebody really does.
“Agent Million knocks on two doors a month. Those are real people, and one day one of them could be you. The £125 is what happens in the meantime, whatever the doorbell does.”
Side by side
£5,000 over 5 years, both ways
| Year | Savings account at 4.21 percent | Premium Bonds at average luck |
|---|---|---|
| 0 | £5,000 | £5,000 |
| 1 | £5,215 | £5,193 |
| 2 | £5,438 | £5,394 |
| 3 | £5,672 | £5,603 |
| 4 | £5,915 | £5,819 |
| 5 | £6,169 | £6,044 |
Two lines this close together is the point. Premium Bonds are not a disaster, they are quietly second. The shaded wedge is the whole argument, and it widens every year you leave it.
Three things this tool will not pretend about
Prizes are tax free. That is worth real money to a higher-rate taxpayer holding savings outside an ISA, and worth nothing at all to someone whose interest already fits inside their Personal Savings Allowance, so the comparison above is closer for some readers than others.
Typical luck runs below the average. Two £1m prizes and a long tail of £100,000 and £50,000 ones drag the mean upwards, and the mean is what this page shows. A typical year lands under it. The gap here is the kind version.
The zero-prize figure is the exact one. It needs no assumptions about the prize distribution at all: it comes straight from NS&I’s published odds for a single £1 Bond, so it is a calculation rather than an estimate. That 6.5% is real.
How this works
Premium Bonds are modelled at NS&I’s prize fund rate of 3.8% (from the July 2026 prize draw), which is the share of everything held that gets paid out in prizes over a year. The zero-prize odds use NS&I’s published 1 in 22,000 chance for a single £1 Bond in a monthly draw, which applies from the July 2026 prize draw (shortened from 23,000 to 1). The £1m odds use 2 jackpots per draw and the 136,975,958,547 eligible £1 Bonds in the July 2026 draw (moves every month), which is a number that changes every month. Both sides compound monthly and assume prizes and interest are left to roll up, so a modelled Bonds balance can drift past the £50,000 NS&I cap in later years, at which point real winnings would have to go somewhere else. Rates on both sides can change at any time, and NS&I has moved this one twice in a year. This is not financial advice. These are ideas to make you a little bit richer.
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