Carats to Grams (ct to g) Converter

Carats to Grams Conversion

The carat (ct) is the standard unit for measuring gemstone and diamond weight. Converting to grams relates precious-stone weights to everyday measurements and reveals the true mass of a jewelry piece.

Conversion formula: 1 ct = 0.2 g (200 mg) exactly — multiply carats by 0.2.

When You Need This

Buying jewelry — understanding gemstone weights
Insurance appraisals — documenting value in metric units
Shipping valuables — calculating package weight
Gemology research — scientific measurement
Customs declarations — traveling with jewelry

How to Convert

The Conversion Formula

One carat equals exactly 0.2 grams (200 milligrams), standardized internationally in 1907. To convert, multiply the number of carats by 0.2. To go the other way, divide grams by 0.2 (or multiply by 5).

grams = carats × 0.2 — for example, 1.5 ct × 0.2 = 0.3 g.

Using the Tool

Enter the value

Type the amount you want to convert into the input field.

Read the result instantly

The converted value appears immediately in the second field — no button to press.

Swap or pick any unit

Press the swap button to reverse direction, or open a dropdown to choose a different unit.

Copy the result

Tap the copy icon next to either field to copy the value for your records.

Worked Examples

Carats	Calculation	Grams
1 ct	`1 × 0.2`	0.2 g
0.5 ct	`0.5 × 0.2`	0.1 g
2 ct	`2 × 0.2`	0.4 g
5 ct	`5 × 0.2`	1 g

Features & Use Cases

Tool Capabilities

Instant Two-Way Conversion

Results update as you type. Use the swap button to reverse the direction in one click.

Any Unit, Any Pair

Searchable dropdowns let you switch to grams, ounces, pounds, stone, tons, carats and more — not just the default pair.

Copy & Quick Reference

Copy either value with one tap, and check the built-in reference table for common conversions at a glance.

Common Use Cases

Diamond Shopping

Engagement-ring diamonds are typically 0.5–1.5 ct. Convert to grams to grasp how little a high-value stone actually weighs.

Jewelry Appraisal

Appraisers and insurers record stone weight in grams for documentation alongside the carat figure.

Shipping & Customs

Customs forms and couriers often need metric weights. Convert carats to grams for accurate declarations.

Gemology Research

Scientific work uses grams. Convert carat measurements to grams for density and material calculations.

Carat ≠ Karat. Carat (ct) measures gemstone weight; karat (K) measures gold purity (24K = pure gold). They sound alike but are entirely different concepts.

Runs in your browser: All calculations happen locally on your device. Nothing is uploaded — fast and private.

Frequently Asked Questions

How many grams are in one carat?

One carat equals exactly 0.2 grams (200 milligrams).

How many carats are in one gram?

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

What is the difference between carat and karat?

Carat (ct) measures gemstone weight; karat (K) measures gold purity (24K = 100% gold). They are unrelated despite the similar sound.

Why is a carat 0.2 grams?

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

How big is a one-carat diamond?

A round one-carat diamond is about 6.5 mm in diameter, yet weighs only 0.2 grams — surprisingly light for such a valuable item.

Does carat weight equal diamond size?

No. Carat is weight, not size. A poorly cut one-carat stone can look smaller than a well-cut 0.9-carat one. Cut quality affects apparent size.

Carats to Grams