Compound Interest Calculator (UK)

A practical “what happens to my money over time?” tool. Includes inflation (“today’s money”), contribution increases, and optional advanced events (lump sums, rate changes, pause/resume contributions).

Anonymous Client-side only Monthly timeline simulation

Inputs

Your starting pot.

Defaults to today.

Add months beyond whole years (0–11).

Nominal return (before inflation). Advanced events can change this over time.

How interest is applied. (Most “normal” calculators assume monthly.)

Used to show “today’s money” values. Example: 3% inflation means £100 in the future buys ~£97 worth of stuff in today’s terms.

Used for the “monthly income at end” estimate (e.g., 4% rule).

Ongoing contributions

Your regular contribution.

Converted into an equivalent monthly amount for the timeline.

If > 0, your contribution amount increases each year by this %. (No checkbox needed.)

Useful if you want to model “I’ll start later” without adding an event.

Advanced mode (optional)

Use events for changes over time: lump sums, withdrawals, rate changes, contribution changes, pause/resume. If you don’t add events, this behaves like a normal compound interest calculator.

Events

Pick what changes at that date.

Applied at the start of the month containing this date.

Some event types are always one-off (e.g., cash deposit). Others persist by definition.

Date Type Value Effect
No events yet.

Disclaimer: Not financial advice. This is an educational estimate. Real returns and inflation vary, taxes matter, and markets don’t move smoothly.