Vimes Utility
Boots Theory cost-per-day with 5-year injustice gap — cheap break, quality last.
Cost per day = price ÷ (lifespan months × 30). Over 60 months, cheap items are bought ⌈60 ÷ life⌉ times. Injustice gap = cheap total − quality total. Timeline shows each cheap break as ✕, quality as one solid bar.
Part of: Saving & Spending Calculators
Before you trust the result
Check the inputs that matter most: dates, rates, units, costs, and any optional fields you skipped. A calculator can only work with the numbers entered here, so use the result as a decision check rather than a final answer when money, health, tax, legal, or safety consequences are involved.
If the result feels surprising, change one input at a time and watch which number moves. That usually shows the real lever behind the decision.
More about this tool
How to use this tool
- Enter cheap option price and lifespan (months).
- Enter quality option price and lifespan.
- Read per-day cost, total replacements, and injustice gap over 60 months.
Examples
Next up
Frequently asked questions
› Why 5 years? Troubleshooting
It's long enough to expose the compounding but short enough to be realistic. Tweak mentally for longer-horizon items.
› What if the quality item also fails?
Lifespan input handles it. Enter realistic expectation, not marketing copy.
Tips & related reading
See the Saving & Spending Calculators hub →Tips & how-tos
Related tools
Subscription, or Buy It Once?
Find the month a monthly subscription overtakes the one-time price — including what your money could have earned instead.
Rent vs Buy Calculator
Estimate the year buying a home becomes cheaper than renting after mortgage interest, maintenance, selling costs, and cash opportunity cost.
Break-Even Calculator
Calculate how many units you must sell to cover fixed costs — break-even quantity and revenue.