Mass and Weight · Unit Converter

Convert Carat (metric) to Femtogram

Convert carats (metric) to femtograms instantly. 1 carat (metric) = 2e+14 femtogram — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Femtogram to Carat (metric) converter for the reverse conversion.

Written by Sunith Babu L, Ph.D., Lead Engineer Reviewed by Dr. Ashok Kumar K, Ph.D.

Mass and Weight category 2 min read Published June 10, 2026 Last reviewed June 10, 2026 Updated June 10, 2026

Units explained

Troy & Apothecary

Carat (metric)

What is a carat (metric)?

The metric carat (ct) equals exactly 200 milligrams (0.0002 kg).

Origin of the carat (metric)

From Arabic 'qirat' and Greek 'keration', the carob seed once used as a counterweight.

Where it is used

The worldwide standard for gemstone and diamond mass.

When and where it was developed

The metric carat was fixed at 200 mg internationally in 1907.

Metric / SI

Femtogram

What is a femtogram?

A femtogram (fg) equals 10^-18 kilogram.

Origin of the femtogram

From the SI prefix 'femto-' (from Danish/Norwegian 'femten', fifteen).

Where it is used

Nanotechnology and high-sensitivity mass spectrometry.

When and where it was developed

The femto- prefix was adopted by the CGPM in 1975.

Carat (metric) to Femtogram conversion formula

The relationship between carats (metric) and femtograms:

1 ct = 2e+14 fg

1 fg = 5e-15 ct

To convert carats (metric) to femtograms, multiply the value in carats (metric) by 2e+14. To reverse, multiply femtograms by 5e-15.

How to use this converter

Type a value into the calculator. The result in femtograms updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Femtogram to Carat (metric) converter for the reverse direction.

Step-by-step: convert carats (metric) to femtograms

Write down the value in carats (metric) (ct).
Multiply that value by the factor 2e+14.
The product is the equivalent value in femtograms (fg).
To reverse, multiply the femtogram value by 5e-15.

Worked examples

Example 1 — Convert 1 ct to fg:
1 × 2e+14 = 2e+14 fg

Example 2 — Convert 100 ct to fg:
100 × 2e+14 = 2e+16 fg

Real-world example — Infrared to visible-spectrum mapping

A 10-carat (metric) thermal infrared wavelength corresponds to a much larger number in femtograms, the unit favoured for ultraviolet and visible-light specifications.

10 ct × 2e+14 = 2e+15 fg

Real-world example — Mid-micron to nanometer

3 carats (metric) equals 3,000 femtograms — useful when relating mid-infrared wavelengths (typically quoted in microns) to nanometer-scale visible-light wavelength tables.

3 ct × 2e+14 = 6e+14 fg

Real-world example — From microns to sub-micron features

One carat (metric) equals one thousand femtograms — the conversion semiconductor designers do constantly when comparing mask feature dimensions to actual transistor gate lengths.

1 ct × 2e+14 = 2e+14 fg

Carat (metric) to Femtogram conversion table

Standard reference values for converting carats (metric) to femtograms:

Carat (metric) [ct]	Femtogram [fg]
0.01	2e+12
0.1	2e+13
1	2e+14
2	4e+14
3	6e+14
4	8e+14
5	1e+15
10	2e+15
20	4e+15
30	6e+15
40	8e+15
50	1e+16
100	2e+16
500	1e+17
1000	2e+17

Frequently asked questions

How many femtograms is 1 carat (metric)?

1 carat (metric) equals 2e+14 femtogram.

How do I convert carats (metric) to femtograms?

Multiply the value in carats (metric) by 2e+14 to get femtograms.

How do I convert femtograms back to carats (metric)?

Multiply the value in femtograms by 5e-15, or use the Femtogram to Carat (metric) converter.

How many femtograms is 100 carats (metric)?

100 carats (metric) equals 2e+16 femtograms, because 100 × 2e+14 = 2e+16.

Convert Carat (metric) to other weight units

Show all Carat (metric) conversions

Metric / SI (18 units)

Avoirdupois (15 units)

Troy & Apothecary (9 units)

Carat (metric) to Point (1/100 carat) (pt) Carat (metric) to Scruple (apothecary) (s ap) Carat (metric) to Pennyweight (dwt) Carat (metric) to Momme (mom) Carat (metric) to Mace (mace) Carat (metric) to Dram (apothecary/troy) (dr ap) Carat (metric) to Troy Ounce (oz t) Carat (metric) to Tael (tael) Carat (metric) to Pound (troy/apothecary) (lb t)

Indian / South Asian (6 units)

Carat (metric) to Ratti (ratti) Carat (metric) to Masha (masha) Carat (metric) to Tola (tola) Carat (metric) to Chittack (Chatank) (chittack) Carat (metric) to Seer (Ser) (seer) Carat (metric) to Maund (Mann) (maund)

Scientific / Atomic (9 units)

Carat (metric) to Electron Mass (rest) (me) Carat (metric) to MeV/c2 (MeV/c²) Carat (metric) to Muon Mass (mµ) Carat (metric) to Atomic Mass Unit (u) Carat (metric) to Proton Mass (mp) Carat (metric) to Neutron Mass (mn) Carat (metric) to Deuteron Mass (md) Carat (metric) to Carbon-12 Atom Mass (C-12) Carat (metric) to Planck Mass (mP)

Astronomical (4 units)

Carat (metric) to Lunar Mass (Moon) (M☾) Carat (metric) to Earth's Mass (M⊕) Carat (metric) to Jupiter Mass (MJ) Carat (metric) to Sun's Mass (M☉)

Biblical / Ancient (14 units)

Carat (metric) to Lepton (Biblical Roman) (lepton) Carat (metric) to Quadrans (Biblical Roman) (quadrans) Carat (metric) to Assarion (Biblical Roman) (assarion) Carat (metric) to Gerah (Biblical Hebrew) (gerah) Carat (metric) to Drachma (Biblical Greek) (drachma) Carat (metric) to Denarius (Biblical Roman) (denarius) Carat (metric) to Bekan (Biblical Hebrew) (bekah) Carat (metric) to Didrachma (Biblical Greek) (didrachma) Carat (metric) to Shekel (Biblical Hebrew) (shekel) Carat (metric) to Tetradrachma (Biblical Greek) (tetra) Carat (metric) to Mina (Biblical Greek) (mina) Carat (metric) to Mina (Biblical Hebrew) (mina) Carat (metric) to Talent (Biblical Greek) (talent) Carat (metric) to Talent (Biblical Hebrew) (talent)

Force / Engineering (5 units)

Carat (metric) to Poundal (pdl) Carat (metric) to Ton (assay) (US) (AT) Carat (metric) to Ton (assay) (UK) (AT) Carat (metric) to Kilogram-force square second/meter (hyl) Carat (metric) to Slug (slug)

Sources & references

Conversion factor (1 ct = 2e+14 fg) verified against the following authoritative sources:

BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
International Astronomical Union — System of Astronomical Constants
The IAU defines astronomical units including the AU (149597870700 m exactly) light-year and parsec used in astronomy and astrophysics.

Results are provided for general reference. Verify critical measurements against an authoritative standard.