How to use the shelf life and expiry date calculator
- Enter the shelf life as a number of days, weeks or months.
- Set the minimum share of life you will accept, and check today's date.
- Add a row for each lot with the date it was made or received.
- Read the lots in expiry order, with the days left, the share of life left and a status for each.
Formula
expiry date = made date + shelf life (months keep the day, or use the last day of a shorter month)
days left = expiry date - today
life left = days left / (expiry date - made date), kept between 0% and 100%
first expired, first out = lots sorted by expiry date, earliest first
A lot with less life left than your minimum is flagged below minimum, and a lot past its expiry date is shown as expired with the days past.
Three lots with a 90 day shelf life
Lots made on August 20, September 15 and October 1, 2026 with a 90 day shelf life expire on November 18, December 14 and December 30, 2026. The lot made on August 20 is used first.
With a shelf life of one month, a lot made on January 31, 2026 expires on February 28, 2026, and one made on January 31, 2028 expires on February 29, 2028, because the day moves back to the end of a shorter month. On December 29, 2026 with a 50% minimum, the first lot has expired 41 days ago, the second has 1 day and 1.1% of its life left so it is below the minimum, and the third has 62 days and 68.9% left.
First expired, first out
Stock that expires first should leave first. Sorting lots by expiry date, not by arrival date, keeps you from holding a long-dated lot while a short-dated one spoils. The share of life left also helps with receiving rules, such as refusing a delivery that already has less than half its life remaining.
To plan reorders around the dates, use the Days of Supply and Stockout Date Calculator. The Date Calculator adds time to a single date and the Weekday Counter Calculator counts weekdays between two dates.
Reading a printed date
Best before and use by dates mean different things, and some products are safe after a best before date while others are not safe after a use by date. This tool only does the date arithmetic. Follow the label, the storage instructions and the rules of your industry.
Assumptions and limits
- The shelf life counts from the made or received date you enter, not from opening.
- A shelf life in months keeps the day of the month where it exists and otherwise uses the last day.
- The life left is linear in time, and the days between made and expiry dates are whole days.
- Storage conditions, opening and handling can shorten real shelf life.
- This is date arithmetic, not food or product safety advice.
Frequently asked questions
Is the expiry date included in the shelf life?
The expiry date is the made date plus the shelf life, and a lot is treated as good through that day. It shows as expired from the next day.
What does the minimum life left do?
It flags lots with less than that share of their life remaining, which is useful for receiving and for rotating stock.
Why do lots made later sometimes expire earlier?
Lots are sorted by expiry date. Different made dates and the same shelf life keep the order, but if you change the shelf life or the made dates, the order follows the dates.
Can I use different shelf lives for different products?
The tool uses one shelf life per run. Run it once for each product.