Olive Oil Freshness Calculator
How long does olive oil last, does it go bad and what do the figures on a lab certificate mean? See how warmth, light and air change an oil, then check any certificate against the extra virgin limits.
How long does olive oil last?
Unopened and kept cool and dark, extra virgin olive oil is at its best within about 18 to 24 months of bottling; the International Olive Council recommends a best-before date no more than 24 months after bottling. Once opened, aim to finish it within about two months. Olive oil does not go off suddenly: it slowly oxidises and loses its fresh, fruity flavour. In time it turns rancid, smelling of crayons, putty or stale nuts.
How an oil changes in the bottle
An illustration, not a prediction. The curves show the direction and relative speed of change described in published studies. Every oil starts differently and is stored differently, so this cannot tell you the age, quality, grade or shelf life of any particular bottle.
Check a laboratory certificate
Enter figures from an olive oil laboratory certificate to see how each one compares with the legal limit for extra virgin olive oil.
This compares each figure with its limit, one at a time. It does not grade the oil: extra virgin also requires a trained tasting panel to find fruitiness and no defects, as well as other tests.
A worked example: our own certificate
Castruriali extra virgin olive oil, 2024/25 early harvest, tested by Laboratorio Genovese (report 2295-2024): free acidity 0.30% (limit 0.8%), peroxide value under 2 meq O₂/kg (limit 20) and total polyphenols of 410 mg/kg.
These figures describe the batch on the day it was tested. See the full results on our laboratory results page.
How long does olive oil last unopened?
Sealed and stored well, extra virgin olive oil keeps its quality for many months. Most producers give a best-before date of 18 to 24 months from bottling; the International Olive Council recommends no more than 24 months.
The harvest date tells you more than the best-before date. Oil from the most recent harvest is the freshest; it is at its most vivid, bitter and peppery in the first months after milling.
How long does olive oil last once opened?
Opening a bottle lets in air; every pour lets in more. Changes that take months in a sealed bottle begin to take weeks. As a rule, finish an opened bottle within about two months, keep the cap on and keep it away from heat and light.
In a 2025 study, a 750 ml amber bottle opened daily and kept in the dark at about 18 °C passed the K232 limit for extra virgin after seven to eight weeks, while its peroxide value stayed within the limit. A smaller bottle you finish sooner keeps more of its freshness.
Does olive oil go bad?
Olive oil does not spoil suddenly. It oxidises gradually: first the fresh grassy and fruity notes fade, then the bitterness and pepper soften and eventually it turns rancid. Heat, light and air all speed this up.
Your nose is the best test at home. Rancid oil smells of crayons, putty or stale nuts and tastes flat and greasy. If it smells like that, it has lost its quality.
What the laboratory figures mean
Producers have their oil tested to show it meets the legal standard for extra virgin. A certificate usually shows these markers:
Free acidity (limit 0.8%): free fatty acids, a sign of the condition of the olives and how quickly they were milled.
Peroxide value (limit 20 meq O₂/kg): the first stage of oxidation.
K232 and K270 (limits 2.50 and 0.22): ultraviolet readings that rise as oxidation products build up. ΔK (limit 0.01) helps detect refined oil.
Total polyphenols (no legal limit): natural compounds behind the bitterness and pepper of fresh oil, which also help the oil resist oxidation.
Extra virgin also requires a trained tasting panel to find fruitiness and no defects, so no single figure decides the grade.
Where to keep olive oil
Somewhere cool and dark, away from the hob, the oven and sunny windows, with the cap firmly on. Our guide on how to store olive oil covers bottles, tins and decanters in more detail.
Questions people ask
How long does olive oil last once opened?
Aim to use an opened bottle within about two months, with the cap back on and the bottle somewhere cool and dark. Each pour lets in air, which speeds up oxidation. In one study, extra virgin olive oil in amber bottles opened every day at about 18 °C passed the K232 limit for extra virgin after seven to eight weeks.
Does unopened olive oil expire?
Olive oil carries a best-before date rather than a use-by date. The International Olive Council recommends a best-before no more than 24 months after bottling. The harvest date, where shown, is the better guide to freshness: the most recent harvest is the freshest.
How can I tell if olive oil has gone bad?
Smell it and taste a little. Oxidised (rancid) olive oil smells of crayons, putty, varnish or stale nuts and tastes flat and greasy rather than fresh, fruity, bitter and peppery. Colour is not a reliable guide.
Should olive oil be kept in the fridge?
There is no need. Cold makes olive oil cloudy or even solid, which is harmless and clears at room temperature. A cool, dark cupboard away from the hob is the best place.
What is a good acidity for extra virgin olive oil?
The legal limit for extra virgin olive oil is 0.8% free acidity, measured as oleic acid. Acidity is a laboratory measure of free fatty acids, not something you can taste; good oils from sound, quickly milled olives usually measure well below the limit.
What is a good peroxide value for olive oil?
The legal limit for extra virgin is 20 milliequivalents of active oxygen per kilogram (meq O₂/kg). Peroxide value measures the first stage of oxidation. A low figure on the day of testing is a good sign, but it should be read alongside K232, K270 and a tasting panel.
What do K232 and K270 mean on an olive oil certificate?
They measure how much light the oil absorbs at two ultraviolet wavelengths, which rises as oxidation products build up. The extra virgin limits are 2.50 for K232 and 0.22 for K270 (or K268), with ΔK no more than 0.01.
Does a greener olive oil mean it is fresher?
Not necessarily. Colour comes from natural pigments and depends on the olive variety, how ripe the fruit was and how it was milled, as well as age. Professional tasters use dark blue glasses so that colour cannot influence them.
How the calculator works. The curves are a teaching illustration on a relative scale of 0 to 100. Their shapes and speeds are chosen to show the direction of change described in the studies below; they are not measurements, are not linked to legal limits and do not predict when any oil will change. The lab checker compares each figure with its legal limit for extra virgin olive oil in the UK and EU marketing standards. This page is about flavour and storage and makes no health claims.
Sources. Conte and colleagues, Foods 2020 (doi:10.3390/foods9030295): temperature and K270 in bottled oil. Alimi and colleagues, European Food Research and Technology 2025 (doi:10.1007/s00217-025-04743-9): bottles opened daily. Donnarumma and colleagues, Applied Sciences 2026 (doi:10.3390/app16073183): phenolic compounds with repeated use. International Olive Council trade standard and storage guidance.