How to Read an IGI Certificate: A Plain-English Breakdown

Answer first

How do I read an IGI certificate quickly?

Start with the report number, then match the shape, carat weight, measurements, colour, clarity, and cut to the seller page. The certificate proves the stone described is the stone being sold; it does not tell you whether the design suits you, whether the setting is well made, or whether the final price is fair.

What actually matters

Report number verification on IGI
Shape, carat weight, and millimetre measurements
Colour, clarity, and cut grades
Whether the certificate is individual or jewellery-level documentation

Carat Theory's take

Use the certificate as a truth check, then use the product details to decide whether the piece is right.

Evidence

Carat Theory uses individual IGI certificates for diamonds over 0.50 carat and jewellery-level IGI certification for smaller accent diamonds.

Editorial standard: Carat Theory editorial policy. Co-Founder: Sahil Meghani.

Learn to read it

A diamond certificate looks intimidating. It is really a spec sheet. You only need to read five lines of it to know what you are buying.

An IGI (International Gemological Institute) certificate is the report of an independent lab that examined the stone - not the seller's opinion. That is exactly why it matters: a third party, with no stake in the sale, describes the stone.

What the certificate says, line by line

Report number: The stone's unique ID. Verifiable on IGI's website.
Type / origin: Should clearly say "Laboratory Grown" for a lab-grown diamond.
Carat (weight): The stone's weight. Remember: it is a weight, not a size.
Cut: The cut quality (Excellent, Very Good...). This is what creates the sparkle.
Colour: From D (colourless) downward. Confirm the stated colour grade against the product page and report.
Clarity: From FL to I. Confirm the stated clarity grade against the product page and report.
Measurements: Dimensions in mm - useful for comparing real face-up size.

The five lines that matter most

If you are short on time, in this order:

Cut - look at this first, it is what gives the sparkle.
Colour - confirm the stated grade.
Clarity - confirm the stated grade.
Carat - the stone's weight.
Report number - note it down to verify yourself.

The rest is secondary.

A certificate does not make a stone beautiful. It only proves that what you are sold is what you are told.

What you can ignore

Do not let every line freeze you. Fluorescence is rarely an issue. Past a point, the eye stops telling colour and clarity apart, which is why many buyers compare colour and clarity only after confirming cut, measurements, and report authenticity.

Check that it is genuine

Take the report number and enter it in IGI's official verifier. The details should match exactly what the seller shows. If the number does not exist or does not match, stop there.

The report, includedPractice reading a certificate on a real one - it ships in the box.The Lumina Pendant$2,100.00 View →

Frequently asked

Does every stone get its own certificate?

At Carat Theory, every diamond over 0.50 carat includes its own independent IGI certificate. Smaller accent diamonds are certified by IGI together at the jewellery level.

Is IGI as reliable as GIA?

Both are independent labs trusted for lab-grown diamonds. What matters is that a third party, not the seller, graded the stone.

Which line should I read first?

Cut. A well-cut stone sparkles; a poorly cut one looks dull, no matter the other grades.

Written by Sahil Meghani, Carat Theory. Updated September 2026.

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