UK Premium Bonds Prize Chance Calculator
Estimate your chance of winning a prize in UK Premium Bonds using official NS&I odds. Provides per-draw and annual probabilities and expected number of monthly wins based on the number of £1 bonds you hold.
- Page updated:
- Jul 14, 2026
- Tool version:
- v1.1.0
Overview
This calculator estimates your chance of winning a Premium Bonds prize using published NS&I odds. It reports:
- probability of at least one win in a single monthly draw,
- expected number of prizes per month (mean), and
- probability of at least one win across 12 monthly draws (one year).
Core inputs
Results
Chance of ≥1 prize per monthly draw
4.08%
Chance of ≥1 prize per year
39.35%
Expected prizes per month
0.0417
Notes
Assumes an illustrative per-£1 monthly win probability of about 1 in 24,000 (p ≈ 0.0000417) and independence between bonds and draws. These are statistical estimates; update the rate to the latest NS&I published odds.
How to read the result
- What it means
- The displayed value is an estimate based on your inputs. It represents the calculated scenario under current assumptions, not a guaranteed amount.
- Calculation limits
- The model uses simplified formulas and cannot account for all variables in your specific case (local regulations, personal conditions, temporal changes).
- Next step
- Use the result as a starting point. Adjust parameters to compare scenarios and validate with a professional when needed.
Glossary+−
- Bond (Premium Bonds)
Each £1 held in Premium Bonds counts as one bond (one entry) in the monthly prize draw.
- Per-bond probability (p)
The probability that a single £1 bond will win any prize in one monthly draw. This value is published by NS&I and can change over time.
- Expected value (mean)
The statistical average number of prizes expected per draw, calculated as N × p for N bonds.
Key takeaways
This tool gives statistical estimates of chance and expected wins for Premium Bonds using a per-£1 monthly win probability.
Always verify the current NS&I published odds and update the calculator constant (p) to keep estimates current.
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Useful links
Worked examples
Example 1 — £1,000 held
Using p = 1/24,000 per £1 per month (default):
Interpretation
With £1,000 held, you have about a 4.17% chance of at least one win in a single monthly draw and about a 45.1% chance of at least one win over a year (12 draws). Expected monthly wins are around 0.042.
Example 2 — £10,000 held
Using p = 1/24,000 per £1 per month (default):
Interpretation
With £10,000, probability of at least one monthly win is roughly 33.2%; across 12 months it's very likely to see at least one win.
Frequently asked questions
Where does the per-£1 probability come from?
NS&I publishes the effective odds of a single £1 bond winning in a monthly draw. This calculator uses a default illustrative value of 1/24,000 per month; check the NS&I site for the current published figure and update the calculator constant if necessary.
Does this guarantee I will win?
No. These are statistical probabilities and expected values. Individual outcomes vary — you may win more or less than the expectation, or nothing at all.
How should I interpret expected monthly prizes?
Expected prizes is the mean number of wins per month. For example, 0.0417 expected prizes per month means on average one prize every 24 months — it is not a prediction for any specific month.
Are bonds and draws independent?
The model assumes independence between bonds and between monthly draws, which is the standard approach for estimating probabilities using published per-bond odds.
Sources & references
- NS&I - Premium Bonds: How the prizes work: https://www.nsandi.com/premium-bonds/how-the-prizes-work
- NS&I - Odds of winning (published information): https://www.nsandi.com/premium-bonds/odds-of-winning
Quality & oversight
- Author
- Ugo Candido, MBA
- Maintained by
- Ugo Candido, MBA
- Page updated
- Jul 14, 2026
- Tool version
- v1.1.0