How Pistash calculates its figures and dates

Your anti-waste score

The product equivalent, the base unit

Every product added has an initial quantity — a 500g jar, six yoghurts, a one-litre bottle. When you mark part of the product as consumed or discarded, Pistash records the fraction involved — 0.5 if you used half a pack of pasta. A product equivalent corresponds to one whole product processed, whether in one go or across several steps.

The monthly calculation

Each month, the score compares consumed and discarded quantities against the initial quantity of each product. A partial action counts right away — consuming 400g then discarding 100g out of a 500g jar gives 80% on that product. The month's score is the weighted average of every product processed that month.

The tiers

A progress tier appears once the equivalent of 5 products has been processed in the month — Getting started below 40%, On track from 40%, Anti-waste pro from 70%, Anti-waste champion from 90%. Below 5 products, the score is shown but not the tier — a single yoghurt thrown away out of two products would drop the score to 50% without that meaning much. It's a motivating marker, with no other effect on your account.

What doesn't count towards the score

• A product removed with the "Delete" action is neither consumed nor discarded — it disappears without affecting the score.
• The price, when you record it, is a reference on the product card but doesn't factor into the calculation.
• The free plan lets you view the last three months of history.

Community statistics

The homepage sometimes shows a banner summarising the impact of all Pistash users. It's based on the same unit as your personal score: the product equivalent.

The global anti-waste rate

The anti-waste rate is the ratio between product equivalents consumed and the total product equivalents processed (consumed + discarded), across the entire history of every Pistash user. A rate of 80% means that, out of 10 products processed, 8 were consumed and 2 were discarded.

The credibility threshold

Below 500 total product equivalents processed, a global figure would be anecdotal and not very representative — it could even be discouraging rather than encouraging, exactly like your personal tier only appears after 5 products in the month. The banner is therefore only shown once this threshold is reached, and appears automatically as soon as it is.

How Pistash estimates a date

Three types of dates

• Use-by date: a safety limit. It's copied straight from the packaging and isn't up for debate.
• Best-before date: a quality guarantee, not a safety one. It can generally be exceeded if the product and its packaging are intact.
• Pistash estimate: a guideline suggested when the product has no printed date, or after opening. It depends on the product's condition and storage.

In the app, each product shows which of these three types applies, and reminder wording adapts accordingly.

For more on the difference between use-by and best-before dates, and on what you can still eat after the date, read our guide Use-by and best-before dates explained.

Where the default durations come from

Pistash relies on an internal database of more than 270 everyday products — mostly food, plus around thirty pharmacy and household items. For each one, it knows the usual storage location, the shelf life before opening, the shelf life after opening, and the type of date the product normally carries (use-by, best-before, or none).

These durations were compiled from public sources: French health authority recommendations, recognised storage guides, and manufacturer information. They were cross-checked against each other and rounded down: when sources disagree, Pistash keeps the shorter duration. This isn't an official database, and no authority has validated it. These are cautious reference points for a product stored in good conditions, not guarantees.

A Pistash estimate is only offered for products with no printed date: fresh fruit and vegetables, bread and pastries, homemade dishes. For a packaged product, the date on the packaging always takes priority: Pistash doesn't suggest a date, you copy it yourself.

After opening

For products with a known post-opening shelf life, the "Open" action marks the product as opened, with a new estimated date counted from the day it was opened; if the date printed on the packaging is sooner, that one is kept. This action is only offered if Pistash has a suitable post-opening duration for the product; otherwise, you enter the date yourself.

Medicine cabinet: a special case

For medicines and health products, Pistash never suggests an estimate in place of the printed date. The post-opening durations in the database (eye drops, saline solution, syrup, sunscreen) match the post-opening periods commonly shown on packaging, but the open-jar symbol and the leaflet remain the only real reference. When in doubt, ask your pharmacist.

The label always wins

An estimate is a guideline, never a permission. If the packaging or manufacturer's instructions state a duration, that's what counts, and you can correct the estimated date at any time on the product's card.

Report an error

If a duration looks wrong to you, let us know through support once signed in (My account > Support). The database is corrected regularly.

The limits of these figures

• The score and statistics only reflect what users record. A product thrown away without being logged doesn't exist for Pistash.
• They measure the activity observed within the app, not a real impact on food waste at the scale of a household or a country.
• Default durations are averages for a healthy product stored in good conditions: they don't account for a poorly set fridge, a break in the cold chain, or the product's condition at purchase.