The errand math: three kids, two parents, one cat, zero extra trips
How one family cut the 'quick run' habit with a whiteboard rule and a receipt — the consolidation math that gave us back our Saturdays.
We didn't set out to build a spreadsheet empire about trash bags. We set out to stop spending Saturday mornings in a parking lot.
The week we actually counted
Three kids, two parents, one cat (an asshole). At some point we counted a normal week: the big grocery run, the "just diapers" dash, the return trip that became a cart of other things, the cat-food emergency (see: asshole), and the Sunday "we forgot trash bags" special.
Five trips. Each one costs about $14.45 — $1.45 in gas (11 mi round trip at 26 mpg, $3.42/gal) and $13.00 in time (52 minutes at $15/hr) before a single item hits the cart. Here's what the habit was costing per year:
Not one of those trips was a decision. Every one was a staple running out unannounced and deputizing a parent.
The whiteboard rule
The fix wasn't an app. It was a rule on the kitchen whiteboard:
If it runs out on a schedule, it arrives on a schedule.
Diapers, wipes, trash bags, detergent, coffee, the cat's food — anything consumed at a predictable rate got moved to auto-delivery, sized to the cheapest per-unit pack, stacked with Subscribe & Save. The biggest current wins on our ledger:
What's left is the good trip
Here's the part that surprised us: we still go to the store — and it's better now. One planned run a week, built around things actually worth choosing in person: produce you can squeeze, the deli counter, whatever the five-year-old is calling a birthday cake this year.
The trips that vanished were never the good ones. Nobody has a cherished memory of aisle 14 at 8:40pm holding one giant thing of detergent.
Start with one
Don't reorganize your life this weekend. Pick the one item that most reliably triggers an emergency run — for us it was diapers, for you it might be litter or coffee — and put just that on a schedule. One deleted trip per month pays for itself immediately; the habit spreads on its own from there.
Then run your own family's numbers on the trip cost calculator — there's a minivan preset, because we know who we're talking to.
Quick answers
How much can consolidating errands actually save?
Every store run you delete saves the full trip cost — gas plus your time, roughly $8 per run at our conservative defaults. A family that goes from eight runs a month to three saves around $480 a year in trip costs alone, before counting the checkout-lane impulse spend that never happened.
What's the easiest way to cut store trips?
Move the predictable re-buys — diapers, trash bags, detergent, pet food — to auto-delivery, and batch what's left into one planned weekly run. The 8pm emergency dash exists because a staple ran out unannounced; staples on a schedule don't run out unannounced.
Isn't this just 'shop online more'?
It's narrower than that: it's 'stop driving for the boring stuff.' The store trip you keep should be for things worth choosing in person — produce, the deli counter, the kid's birthday cake. Trash bags were never worth a parking lot.