Premium Bond Calculator

Estimate prize chances from your bond holdings quickly. Model tax and inflation effects across draws. Plan contributions smarter with clear expected returns each month.

Calculator Inputs

Use the responsive grid: 3 columns on large screens, 2 on medium, 1 on mobile.

Affects display only.
Total premium bond value you own now.
Optional: added each month in the projection.
1 to 30 years supported.
Choose the method that matches the product you follow.
Expected prizes = holdings × rate.
Value per unit used in the odds.
Expected wins per draw = units ÷ N.
Used to estimate annual prize totals.
Often 12 for monthly draws.
After-tax prizes = gross × (1 − tax).
Used to compute real (inflation-adjusted) value.
A projection assumption, not guaranteed.
Used for 5th/median/95th percentile estimates.

Example Data Table

Sample inputs and what this calculator reports. Replace values with your own product details.

Scenario Holdings Method Key Inputs Key Output
Rate example Rs 50,000 Prize rate Prize rate 10%, tax 0% Expected prizes ≈ Rs 5,000 yearly
Odds example Rs 50,000 Odds and average prize Denom 100, odds 1 in 24,000, avg prize 500 Expected prizes ≈ wins × average prize

Formula Used

Prize rate method

Expected annual prizes (gross) = Holdings × (Prize rate ÷ 100)

Expected annual prizes (after tax) = Expected gross × (1 − Tax rate ÷ 100)

Odds and average prize method

Units = Holdings ÷ Denomination

Expected wins per year (λ) = (Units ÷ Odds N) × Draws per year

Expected annual prizes (gross) = λ × Average prize

Chance of at least one win (annual) = 1 − e−λ

Inflation adjustment

Real value in year t = Nominal value ÷ (1 + Inflation)t

How to Use This Calculator

  1. Enter your current holdings and optional monthly contribution.
  2. Select a method: prize rate, or odds with average prize.
  3. Fill the method-specific fields based on your bond scheme.
  4. Add tax and inflation for after-tax and real comparisons.
  5. Enable reinvestment if you want a growth-style projection.
  6. Press Calculate to view results above the form.

Expected prize value as a return proxy

This calculator estimates the average prize money your holding could generate over a year. In prize-rate mode, expected prizes equal holdings multiplied by an annual rate. In odds mode, expected wins are modeled from units, draw frequency, and “one in N” odds, then multiplied by an average prize.

Why outcomes vary even when averages look stable

Premium bond prizes are lumpy. Many holders see long stretches with no wins, while a small share captures large prizes. That is why the results panel shows both an expected value and, in odds mode, simulated percentiles. The 5th percentile reflects a pessimistic year, the median reflects a typical year, and the 95th percentile represents a strong year.

Linking odds, units, and win probability

In odds mode, units equal holdings divided by denomination. Expected annual wins λ equals (units divided by N) times draws per year. The chance of at least one win is 1 minus e to the power of negative λ. As λ rises, the probability quickly approaches 100%, but the prize total still depends on prize sizes.

Tax and inflation for decision quality

Prizes may be taxed in some jurisdictions, so the calculator applies an optional tax rate to convert gross to after-tax expectations. Inflation then converts nominal projections to real purchasing power. A nominal gain can still be a real loss if inflation is higher than the expected after-tax return.

Projection with contributions and reinvestment

The projection table adds monthly contributions and can reinvest expected after-tax prizes into the balance. Reinvestment is a planning assumption, not a guarantee. Use it to compare “cash-out prizes” versus “compounding prizes” and to understand how steady contributions change the expected prize base over time.

Reading the graph and refining inputs

The Plotly chart visualizes nominal and real end balances by year from the projection. If the real line declines while nominal rises, inflation is eroding value. Improve realism by adjusting denomination, odds, average prize, draws per year, and tax. Update the holding period to match your planning horizon and export CSV or PDF for reporting. For scenario testing, run multiple assumptions and compare the return percentages beside probability metrics to gauge risk tolerance for you.

FAQs

1) What does “expected prizes” mean here?

It is the long‑run average prize amount implied by your inputs. Actual results can be higher or lower in any year, especially with small holdings or low win rates.

2) Which method should I use: prize rate or odds?

Use prize rate when you have an official annual prize fund rate estimate. Use odds mode when you know denomination, draw frequency, odds per unit, and a reasonable average prize.

3) Why can the real return be negative?

Real return adjusts for inflation. If your after‑tax expected return is below inflation, purchasing power falls even if nominal expected prizes are positive.

4) How does reinvestment affect the projection?

When enabled, after‑tax expected prizes are added to the balance each year. This increases future expected prizes because the expected prize base becomes larger.

5) Are the simulation percentiles guaranteed?

No. They are a statistical illustration using a Poisson win model and your average prize assumption. They help you understand variability, not to predict exact results.

6) Can I export the full projection table?

Yes. After you calculate, use Download CSV for the projection data, or Download PDF for a report containing results and the visible table.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.