How to read a compound interest table
Start with the yearly breakdown. It shows the opening balance, added contributions, interest for the year, cumulative interest, and ending balance.
Year-by-year
Compound Interest Table Calculator
Inputs & Actions
Preset example: £10,000 over 10 years
Used for the year-by-year breakdown and summary.
Use a negative amount for regular withdrawals.
Used when the rate type is Nominal APR.
Tip: start with ≤ 20% to keep the table compact, then widen.
e.g., 0.25, 0.5, 1
Values update live when you change inputs. CSV exports include the rate comparison table and yearly breakdown.
Chart & Summary
Summary: —
Final balance—
Principal—
Total contributions—
Total interest—
Effective annual rate—
Growth multiple—
Best / worst rate outcome—
Approx. doubling time—
Advertisement
Compound Interest Tables
| Year | Starting Balance (£) | Contributions (£) | Interest Earned (£) | Total Interest (£) | Ending Balance (£) |
|---|
| Rate (%) | EAR (%) | Growth Factor | Total Contributions (£) | Interest Earned (£) | Final Amount (£) |
|---|
Worked Example
Using the default values, the calculator starts with £10,000, runs for 10 years, and uses a selected rate of 5% EAR/APY with no regular contributions.
A = P(1 + r)t
A = 10000 x (1 + 0.05)10 = 16288.95
The final balance is £16,288.95. Interest earned is £6,288.95, because no extra contributions were added.
Methodology and Assumptions
How calculations run
All calculations run in your browser. The page does not send your principal, rates, or contribution settings to a server.
Rounding
Internal calculations use full JavaScript number precision. Displayed currency values are rounded to 2 decimal places and percentages to practical table precision.
Review note
Prepared by Starlight Tools. Last reviewed: 23 June 2026.
Disclaimer
Results are illustrative only and are not financial advice. They exclude taxes, fees, inflation, account limits, investment risk, and provider-specific rules.
Compound Interest Formulas
Final amount: A = P(1 + r)t
A is final amount, P is principal, r is the effective annual rate, and t is years. Use this when there are no regular contributions.
Interest earned: Interest = A - P - C
C is total net contributions. If withdrawals are entered as negative contributions, they reduce C.
Nominal APR to EAR/APY: EAR = (1 + rnom / m)m - 1
rnom is nominal APR as a decimal and m is compounding periods per year.
Continuous compounding: A = Pert and EAR = er - 1
Use continuous compounding when interest is modelled as compounding at every instant rather than a fixed number of periods.
Doubling time: Years = ln(2) / ln(1 + r)
The summary also shows the familiar Rule of 72 approximation as 72 / rate% when the rate is positive.
Recurring contribution future value: FV = PMT x (((1 + i)n - 1) / i)
PMT is each contribution, i is the periodic rate, and n is the number of contribution periods. Beginning-of-period contributions are multiplied by (1 + i). This calculator simulates the schedule so annual contribution increases and partial final years are handled consistently.
How to Use the Results
APR vs APY
APR is the stated rate. APY or EAR is what that rate becomes after compounding frequency is applied.
Rate meaning
Why frequency matters
With the same nominal APR, more frequent compounding produces a higher effective annual rate, though the difference may be small at normal savings rates.
Frequency effect
Common mistakes
Do not compare a nominal APR directly with an APY, and do not forget taxes, fees, inflation, withdrawal timing, or contribution limits.
Assumptions
Compound Interest FAQ
How is compound interest calculated?
For a lump sum, compound interest uses A = P(1 + r)t. With contributions, each deposit is added at its selected timing and then compounded for the time it remains invested.
What is the difference between APR and APY?
APR is the stated annual rate before compounding. APY, also called EAR, is the effective annual return after compounding.
Is monthly compounding better than annual compounding?
For the same nominal APR, monthly compounding gives a slightly higher APY than annual compounding because interest is credited more often.
Are contributions included?
Yes. Add a regular contribution, choose weekly through annual timing, apply an annual increase if needed, and choose whether deposits happen at the beginning or end of each period.
How do I use a compound interest table?
Use the yearly table to inspect the path of growth over time. Use the rate comparison table and chart to compare what different returns would mean for the final balance.
What does the Rule of 72 mean?
The Rule of 72 estimates doubling time by dividing 72 by the annual percentage return. A 6% return suggests roughly 12 years to double before fees, taxes, and other real-world effects.
Is this financial advice?
No. This calculator is an educational modelling tool and does not provide personalised financial advice.