See what loose change really adds up to.

Spare change investing - rounding up every card transaction to the nearest pound and investing the difference - sounds trivial. A 60p round-up on a 2.40 coffee feels like nothing. But do it 6-8 times a day, and it's 3-5 a day, 90-150 a month, 1,100-1,800 a year. Over 20 years at market returns, that compounds into something meaningful.

This calculator takes a daily average round-up amount and projects it forward as a standard monthly investment. At 3 a day for 30 years with a 7% real return, you'd end up with roughly 110,000 - from money that felt like loose change. The compounding is what makes the number surprising, not the daily amount.

The approach works best as an add-on to real saving, not a replacement. Someone saving nothing else won't hit financial goals on round-ups alone. Paired with a proper pension or tax-advantaged savings account contribution, it's a low-friction extra channel that captures money people would otherwise fail to save.

Run it with sensible defaults

Using average daily round-up of 3, time horizon of 20, annual investment return of 7%, the calculation works out to 46,883.40. Nudge the inputs toward your own situation and the output recalculates instantly. The defaults are meant as a starting point, not a recommendation.

The levers in this calculation

The inputs — Average Daily Round-Up, Time Horizon, and Annual Investment Return — do not pull with equal force. The rate and the time horizon usually dominate — compounding means a small change in either reshapes the final figure more than a similar shift in contribution size. Test this by doubling one input at a time.

How the math works

Daily amount × 30 gives monthly contribution. Standard future-value annuity formula applied with monthly compounding. The working is transparent — you can verify every step yourself in the formula section below. No black box, no opaque "proprietary model".

Making this stick

The number the tool produces is only useful if you act on it. The simplest habit that works: automate the savings transfer on payday, then spend what's left. Everyone who's told you "pay yourself first" was right; the math here is what makes the first number concrete.

What this doesn't capture

Budgets are snapshots of intent. Real spending includes irregular costs: birthdays, one-off repairs, the occasional bad week. Tracking actual spending for a month before fixing any budget usually reveals 10–20% that didn't make the original plan.