Shelf Life Calculator (After Opening)

Shelf life after opening (sometimes called secondary shelf life) is how long a product stays safe and acceptable once its packaging has been opened, which is often much shorter than the printed use-by or best-before date. This calculator works from that opened-product window: you enter how many days the product keeps after opening, how many days have already passed, and a warning threshold, and it tells you the days remaining and whether the item is valid, expiring or expired.

Days remaining is the validity in days minus the days elapsed since opening. The share of shelf life used is days elapsed divided by validity, times 100. The status is expired when days remaining is below zero, expiring when days remaining is at or below your warning threshold, and valid otherwise. These are indicative values to support good rotation, not a guarantee of safety.

The warning threshold is the number of days before expiry at which you want the product flagged as expiring, so staff use it first or remove it before it lapses. For example, a one-day threshold on a three-day product flags it on its final day. Setting a sensible threshold turns the calculator into a simple FIFO (first-in, first-out) aid for the fridge.

Once a product is opened, the shorter of the two windows applies: the product must still be within its printed date and within its after-opening window. This calculator focuses on the after-opening window; you must also respect the original use-by date on the package. Where guidance differs, follow the manufacturer instructions and the local regulations in force.

No. The result is an indicative aid for rotation and should be backed by physical labels recording the opening date, plus your HACCP procedures and the manufacturer's storage instructions. Always check the local regulations that apply to your business.