What The Premium Bonds Calculator Works Out
- Average winnings per year: your holding multiplied by the prize fund rate, 4.35% from the September 2026 draw. Premium Bonds pay no interest; NS&I pools what the interest would have been and raffles it monthly, so this is the mean return across all 130-billion-odd bonds, not anyone's likely experience.
- How often you win: each GBP 1 bond has odds of 21,000 to 1 in each monthly draw, so GBP 1,000 expects about 0.57 prizes a year, roughly one every 21 months. Bonds enter the draw only after a full calendar month: December purchases first play in February.
- Same money in savings: the holding at your comparison rate, guaranteed but taxable above the Personal Savings Allowance (GBP 1,000 for basic-rate taxpayers, GBP 500 for higher-rate, nil for additional-rate).
- Chance of winning nothing in a year (advanced): (1 - 1/21,000) raised to the power of your bonds x 12 draws. A GBP 1,000 holder has around a 56% chance of a prize-free year; GBP 50,000 holders almost never go a year without one. That is the statistical fine print behind "my nan wins constantly" and "mine never win anything" both being true.
- Typical year with median luck (advanced): the expected number of prizes rounded to a whole number, valued at GBP 25 each because roughly nine in ten prizes are the minimum. Two million-pound prizes a month and a pyramid of large prizes pull the mean above what the median holder sees, and the gap widens as holdings shrink.
- Savings rate needed to beat the bonds (advanced): the prize rate divided by (1 - your tax rate): the gross rate a taxable account must pay to match a tax-free mean. A 4.35% tax-free return beats a 7.9% gross rate for a 45% taxpayer, which is why the bonds suit higher earners who have filled their ISA and Personal Savings Allowance.
- Over several years (advanced): expected winnings for your chosen period, with prizes either reinvested as new bonds (compounding the holding towards the GBP 50,000 cap) or paid out, against net savings interest compounded at your rate. Add inflation to see what the bonds plus winnings would be worth in today's money; in zero-win years inflation eats the capital.
- Prize fund rate override (advanced): test an announced rate change, since NS&I moves the rate several times a year. Backing is HM Treasury, above the GBP 85,000 FSCS ceiling, and money is accessible within days. Unclaimed prizes run to tens of millions of pounds, so the NS&I prize checker is worth a yearly ritual.
Rates: NS&I: Premium Bonds.