Work out monthly shopping list cost instantly with clear inputs, formula shown and shareable results.
Weeks do not divide evenly into months, so multiply weekly spending by 4.348 (52 divided by 12) rather than 4. Using 4 understates annual grocery spending by about 8% — several hundred pounds a year for a typical household.
Monthly grocery cost
monthly = weekly x 52 / 12 + monthly items; next year = monthly x (1 + inflation)
A year has 52.18 weeks, so a month averages 4.348 weeks. Using 4 misses roughly four weeks of shopping across the year.
Roughly. Households of one spend more per head because of packaging and waste, so comparisons across household sizes need care.