Career-long compound cost of buying lunch vs packed lunch.

8 daily lunch - 3 packed lunch = 5/day. Over 230 working days and 30 career years invested at 7%, the savings compound to roughly 116,400. Not about hating lunch — about recognising that daily small premiums are meaningful lifetime money when compounded.

What the result means

Primary is compound future value. Secondary shows total cost over the period, compound growth, and the monthly drawdown at 4% the final pot would support.

Hybrid realism

Few people pack lunch every day. 3 of 5 days packed = 40% saving on bought lunches. Use your realistic mix — entering the full bought cost overstates the change most people would actually make.

Quick example

With daily lunch cost of 8 and working days per year of 230 (plus annual return of 7% and career years remaining of 30 years), the result is 173,807.85. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.

Which inputs matter most

You enter Daily Lunch Cost, Working Days per Year, Annual Return, and Career Years Remaining. Frequency and unit price pull the total in different directions. The biggest surprise for most people is how small recurring amounts compound into large annual figures — that's where this calculation earns its keep.

What's happening under the hood

Annual spend is daily cost times working days. FV of annuity with annual compounding. Converts to one-year contribution assumption for simplicity. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.

Why the behavioural angle matters

Most personal finance mistakes are behavioural, not mathematical. You know the math; the hard part is acting on it consistently. Calculators like this one are useful because they externalise a private feeling into a public number — and public numbers are easier to argue with than vague feelings.

What this doesn't capture

Behaviour-adjacent math is always an approximation. Human habits are lumpy and context-dependent; the figure here assumes steady behaviour which is a simplification. Treat the output as a prompt for thinking rather than a precise prediction.