In October 2026 a cloud outage took card payments and banking apps offline at several European banks (reported on the Hacker News front page). Shops that take only cards stop; the cash in a drawer at home is what still works.
If the cards stopped working for a week, which day would the tin run dry?
List what your household would still need to pay in cash for seven days. Each day gets an envelope, filled in order from the tin. Then put your savings in layers - the tin, instant-access, notice, longer-term - and see them in months of essentials against a rule-of-thumb range. One run turns it into a plan.
1 The week in cash
When: daily, twice a day, once (Monday), 3x, weekdays, weekend, every other day, Tue-Thu, day 4, days 2-4, or day names like Tue, Fri. The amount is for each time.
2 Seven envelopes
- Full - the tin covers the day
- Short - the tin runs out that day
- Dry - nothing left for it
3 The layers
The tin is the cash above. Instant-access: savings you can move today. Notice: days to weeks to reach. Longer-term: fixed terms and anything slower.
4 Ask for the plan
The verdict follows a fixed rule: exposed if the tin covers fewer than 3 days or the tin and instant-access hold less than a month of essentials; ready if the tin lasts all 7 days and the layers reach the low end of the range; thin otherwise. The model keeps the page's numbers, names no bank or product, and adds nothing your lines and notes do not say.
5 Kept plans
How the numbers are worked out
Each line lands on its days, Monday to Sunday; its amount is per time. The envelopes are filled in day order from the cash in the tin, so the first envelope the tin cannot fill is the day it runs dry, and the shortfall is the week's need minus the tin. The layers are added up and divided by a month of essentials, rounded down to one decimal. The ranges - 3 to 6 months for two or more steady incomes, 6 to 9 for one steady income or variable pay, 6 to 12 for self-employed or retired households - are common rules of thumb, shown as estimates, not advice. Nothing here moves money or knows your bank; it is arithmetic on what you typed.