Reference

Next service: miles and months, whichever comes first

Enter one item from your schedule, when it was last done and how much you drive. The calculator works out when it falls due by miles and by months, and which comes first.

Service (from your schedule) Interval in miles (from your schedule) Interval in months (blank if your schedule gives miles only) Odometer at last service Months since last service Odometer now Miles a year (from setup, or your own estimate)

Assumptions behind the numbers

The rule is the one maintenance booklets print: an item is due at the mileage or the time interval, whichever comes first (Toyota's 2025 warranty and maintenance guide states it that way).
Months left by mileage assumes you keep driving at the miles a year you entered, spread evenly. A long trip or a quiet winter moves the date.
A blank months interval means the schedule gives miles only, so only the mileage is used. A blank miles interval means time only.
If your car has an oil life monitor, its reading replaces this for the items it tracks, and some makers still require an oil change at least once a year (Chevrolet and Honda say so for their monitors).
This calculator does not know your car's schedule. The interval you enter is the only schedule it uses.

Limits

The calculator applies the interval you typed. It does not know your car's schedule, whether your driving counts as severe, or what your oil life monitor reads. Your owner's manual and your monitor decide what is due; Your maintenance schedule shows how to read them.