How it works
- start date
- the day it was made or opened
- shelf life
- how long it keeps, in days, weeks, months or years
- expiration date
- the day it is no longer good
Shelf life depends entirely on the product, so read it off the label or the manufacturer. "Best before" is about quality and "use by" is about safety; for anything you eat or take, follow the stricter of the two.
Frequently asked questions
How do I calculate an expiration date?
Add the shelf life to the date it was made or opened. Enter both above and the tool gives the expiry date and the days left.
What is the difference between best before and use by?
Best before is about quality, the food is safe after it but may not be at its best; use by is about safety, and you should not eat food after it.
Does "opened" change the date?
Often, yes. Many products have a shorter shelf life once opened, printed as a period-after-opening, so use that shorter figure when the item is open.
How are months counted?
By the calendar, so a shelf life of 6 months lands on the same day number six months later, adjusting for month lengths and leap years.
Related conversions
Counting down instead? Days until a date tells you how long is left before a given expiry or deadline. For food specifically, best before date frames the same shelf-life sum around quality dates.