Olive Maturity Index Explained – Why It’s So Important

Olive Knowledge is a part of Amazon Associates. As an Amazon Associate, we earn from qualifying purchases. Read our Affiliate Disclosure to learn more.

There are many methods to determine the ripeness of olives, but one method stands out a lot – the Olive Maturity Index.

In today’s article, I’ll show you the olive maturity index and why you should use it when deciding if it is a good time to gather olives from the trees.

Key Takeaways:

  • The Olive Maturity Index is a widely accepted method for determining the average ripeness degree of olives.
  • The Olive Maturity Index is also called the Jaen Index because it was invented in Jaen, Spain.
  • The maturity index ranges from 0 to 7, where 0 represents completely green fruits, and 7 represents fully ripe olives.
  • The ideal OMI is between 2.5 and 4.5.

What Is the Olive Maturity Index

why is olive maturity index so important

The Olive Maturity Index was invented in Jaen, Spain, in 2011. Many olive growers use it to determine the best time for harvesting olives in order to get the highest-quality olive oil. Its purpose is to show when olive fruits are full of quality oils that’ll yield larger amounts of oil per 1kg of fruit.

At first, it was done by cameras and computer programs, but the best thing is that anyone can calculate it by themselves (I’ll show you a way in just a minute).

The Olive Maturity Index has classification groups of olive fruits based on skin and flesh color. There are 8 groups, usually classified from 0 to 7 or A to H. Below is a table that explains each group.

Adeep green color and hard fruit
Byellow to green color, the fruit is a bit softer
Cless than half of the fruit skin is turning purple or black
Dmore than half of the fruit skin is turning purple or black
Ethe entire olive skin is purple or black, but less than half of the olive flesh turns purple
Fthe whole of the olive skin is purple or black, but with more than half of the olive flesh turns purple
Gthe whole of the olive skin is purple or black, but more than half of the olive flesh turns purple
Holive skin is entirely purple or black, and the flesh is purple to the pit

The method works by randomly picking 100 olives from various trees and dividing them into 8 categories (according to fruit skin and flesh color). When the olives have been divided into categories, you should count the olives in each category and then use the formula below.

Olive Maturity Index Formula: (A*0+B*1+C*2+D*3+E*4+F*5+G*6+H*7)/100

Why This Index Is Important

Knowing the maturity index of olives is extremely important for olive growers who want to produce high-quality olive oil. Harvesting olives only a few days too soon or a few days too late can play a significant role in olive oil quality.

I think that the maturity index is important because it’s so much better than other methods of determining the average olive fruit ripeness. Many people still use different methods, but these methods don’t show any mathematical number you can rely on.

The olive maturity index is mathematical and excludes human error, and that’s the biggest reason why more and more olive growers are using it before going to harvest olives.

How To Calculate the Olive Maturity Index

To calculate OMI (Olive maturity index), go to your olive farm and randomly pick 100 olives. Don’t pick all 100 olives from one tree; make sure to pick them from various trees. Now that you have 100 randomly picked olives, you should divide them into eight categories I showed you above. Just make sure to check the description of each category and divide olives according to that.

Now that all the olives are separated into categories, it’s time to do the math. Count the number of olives in each category, you’ll write numbers of olives in each category instead of letter of that category. Let’s repeat the formula for maturity index: (A*0+B*1+C*2+D*3+E*4+F*5+G*6+H*7)/100 = Maturity Index.

For instance, if you have 11 olives in category A, and 7 olives in category B, 14 olives in category C, you’ll write those numbers instead of letters. Example: (11*0+7*1+14*2…., and so on). I wrote the full example in this article.

When you calculate that, the number you get is the maturity index, which shows the average ripeness of olives on your olive farm.

I know many people don’t like to calculate, especially such long formulas, so I decided to make an online calculator that you can use to calculate the olive maturity index. It’s straightforward to use, and I wrote you instructions, too, so you can’t make any mistakes. Click the link below to access the calculator.

Click Here To Open The Olive Maturity Index Calculator

What Is Good Olive Maturity Index

Many experts agree that a good olive maturity index result is anywhere between 2.5 and 4.5. In reality, those are a bit stretched numbers, especially the 4.5 one.

Studies have shown that the 3.5 maturity index is ideal for earlier olive varieties, while for the late varieties, it’s between 2.5 and 3.0. Also the best maturity index can also vary depending on the exact olive type, whether it’s a late or early one.

good olive maturity index

Personally, I like to pick my olives whenever the olive maturity index is around 3.0. That way, I know I’ll get satisfactory amounts of olive oil from one pound of olives, and I also know that the oil will be of high quality.


I hope that by now, you know how crucial the olive maturity index is and why you should use it to calculate the average fruit ripeness in your olive farm. I tried to give you a thorough explanation while staying easily understandable so that anyone can read and fully understand it.

Actually, there’s nothing that could confuse you, especially if you’ll be using an online calculator I made. It’s so simple, and it takes only a minute to calculate the maturity index (of course, if you have olives divided into needed categories).

As I always say, new stuff is invented all the time, and it’s up to us whether we will use it. The maturity index is a fantastic thing, and every olive grower should know how to use it and, in the end, use it to determine the right time to pick olives.