What Is Carat to Grams Conversion?

The carat (ct) is the standard unit for measuring gemstone and diamond weight. Converting to grams helps relate precious stone weights to everyday measurements and understand the actual mass of jewelry pieces.

When You Need This Conversion

Buying jewelry — Understanding stone weights
Insurance appraisals — Documentation in metric
Shipping valuables — Package weight calculations
Comparing stones — Across different measurements
Scientific work — Gemology research
Customs declarations — International travel with jewelry

The Conversion Factor

One carat equals exactly 0.2 grams (200 milligrams). This was standardized internationally in 1907. To convert, multiply carats by 0.2.

Carat vs Karat

Don't confuse them! Carat (ct) measures gemstone weight. Karat (K or kt) measures gold purity (24K = pure gold). They're completely different.

How to Convert Carats to Grams

Using This Converter

Enter weight in carats
See the gram equivalent instantly
Use swap to convert grams to carats
Copy the result for documentation

The Simple Math

Multiply by 0.2 (or divide by 5):

0.5 ct = 0.1 g (100 mg)
1 ct = 0.2 g (200 mg)
2 ct = 0.4 g (400 mg)
5 ct = 1 g
10 ct = 2 g

Common Diamond Sizes

0.25 ct (quarter carat) = 50 mg
0.5 ct (half carat) = 100 mg
1 ct (one carat) = 200 mg
2 ct = 400 mg (quite large)
5 ct = 1 gram (exceptional size)

Perspective

A 1-carat diamond weighs just 0.2 grams — about the weight of a small paperclip. Despite the tiny mass, carat size dramatically affects value.

Features & Use Cases

Instant Bidirectional Conversion

Convert carats to grams or grams to carats instantly. Essential for jewelry professionals and buyers alike.

Common Use Cases

Jewelry Shopping

Understand what a 1.5 carat ring actually weighs in familiar terms. Helps contextualize gemstone sizes.

Insurance & Appraisals

Insurance documents may require metric weights. Convert carat weights for accurate documentation.

Shipping & Customs

Declare jewelry weights in grams for international shipping and customs forms.

Price Comparison

Compare gemstone prices per gram across different stone types and qualities.

Jewelry Making

Craftspeople need gram weights for setting stones and calculating total piece weight.

Reference Table

Common carat weights from 0.25 to 10 carats with their gram and milligram equivalents.

Frequently Asked Questions

How many grams in a carat?

One carat equals exactly 0.2 grams (200 milligrams).

How many carats in a gram?

One gram equals 5 carats. A 1-gram gemstone is exceptionally large.

What's the difference between carat and karat?

Carat (ct) measures gemstone weight. Karat (K) measures gold purity (24K = 100% gold). They're unrelated despite similar pronunciation.

Why is a carat 0.2 grams?

Historically, carat weight came from carob seeds used as counterweights. In 1907, the metric carat was standardized at exactly 200 mg for consistency.

How big is a 1-carat diamond?

A round 1-carat diamond is about 6.5mm in diameter. It weighs just 0.2 grams — surprisingly light for such a valuable item.

Does carat weight determine diamond size?

Carat is weight, not size. A poorly cut 1-carat diamond may look smaller than a well-cut 0.9-carat stone. Cut quality affects apparent size.

Carats to Grams