Exagram To Kilogram Converter

1. Leave the mode on Exagrams to kilograms, or switch to kg to Eg to go back.
2. Enter the mass. Decimals such as 6.69 Eg work, and so does e-notation such as 2.4e15 kg.
3. Read the kilograms at once. The cards add tonnes, gigatonnes, petagrams, zettagrams and a power-of-ten form.

An exagram (symbol Eg) is a metric unit of mass equal to 10^18 grams, which is 10^15 kilograms. The name joins the SI prefix exa, meaning 10^18, to the gram.

Mass prefixes attach to the gram, not the kilogram. NIST SP 330 states that multiples of the unit of mass are formed on the name gram and the symbol g. That is why the unit is an exagram and not a petakilogram.

Exa is one of the younger prefixes. The CGPM added peta and exa together in 1975, as the BIPM resolution list and the NIST prefix history both record. Its symbol is a capital E, and the word for 10^18 is one quintillion.

You will rarely see Eg printed. Planetary scientists write the same masses as a number times 10^15 kg. An exagram is simply the SI name for that column heading.

You multiply by 10^15, because exa is 10^18 g, kilo is 10^3 g, and 10^18 / 10^3 = 10^15.

1. Write the exagrams, for example 6.69.
2. Move the decimal point 15 places to the right, adding zeros as needed: 6.69 becomes 6,690,000,000,000,000.
3. Label it kg. In scientific notation you add 15 to the exponent, so 6.69 x 10^0 Eg becomes 6.69 x 10^15 kg.

The tool shifts the decimal point of the number you typed instead of doing floating point math, so the digits you enter come back exactly. The scientific notation calculator helps if you want to check the exponent step by hand.

A small moon. NASA gives Phobos a mass of 10.6 x 10^15 kg. That is 10.6 Eg, or 10,600,000,000,000,000 kg written in full.

An asteroid. NASA lists 433 Eros at 6.69 x 10^15 kg. 6.69 Eg x 10^15 = 6,690,000,000,000,000 kg, which is 6,690 Pg.

Reverse. Deimos has a mass of 2.4 x 10^15 kg. Divide by 10^15 to get 2.4 Eg. Phobos is about 4.4 times heavier.

A planet-wide total. The atmosphere of Earth has a total mass of 5.1 x 10^18 kg. That is 5,100 Eg, or 5.1 Zg.

The factor of 10^15 never changes. What changes the meaning of your number is how the source wrote the mass and how well that mass is known.

The Power of Ten in the Source

NASA tables put the exponent in the column heading, such as Mass (10^15 kg). A value of 10.6 in that column is 10.6 Eg, but the same 10.6 under a 10^24 kg heading is a planet.

Measured or Estimated Mass

The NASA asteroid fact sheet says most of its mass values are only rough estimates. Converting 100 Eg for Ida gives 18 digits, but only the first one or two carry meaning.

Upper or Lower Case

Eg is exa. There is no lowercase e prefix, and EG is not a unit. A capital P (peta) or Z (zetta) in place of E changes the mass by a factor of 1,000.

Short Scale Number Names

NIST names 10^18 one quintillion and 10^15 one quadrillion. Those are US short scale names. The power of ten is the safe way to write the value for readers in other countries.

An exagram sits between the petagram, which is 1,000 times smaller, and the zettagram, which is 1,000 times larger. The NASA figures below show what falls in that range.

Small moons and mid-sized asteroids land between 1 and 1,000 Eg. The atmosphere needs zettagrams. The hydrosphere, which is all the water on Earth, is about 275 times the mass of the atmosphere. Ceres alone holds about 41 percent of the estimated mass of all asteroids.

Carbon-cycle budgets use the smaller unit. The petagram to kilogram converter covers those gigatonne figures.

Reading Planetary Fact Sheets

Moon and asteroid tables list mass as a number times 10^15 kg. Kilograms in full let you drop the value into a spreadsheet without tracking the heading.

Plugging Masses into SI Formulas

Gravity, density and orbit equations expect kilograms. A mass given as 10.6 Eg becomes 1.06 x 10^16 kg before it goes into the formula.

Checking Prefix Homework

Physics and chemistry courses ask students to move between prefixes. The cards show the petagram, zettagram and tonne forms side by side so each step is visible.

Each row is computed from 1 Eg = 10^15 kg = 1,000 Pg = 1,000 Gt. The rows for 2.4, 6.69, 10.6 and 5,100 Eg match the NASA examples above.

For pound figures, the kg to lbs converter takes the kilogram column straight across.

1. Using 10^18 for Kilograms

10^18 is the number of grams in an exagram. For kilograms the factor is 10^15.

2. Miscounting the Zeros

Fifteen zeros are easy to slip. Check with the scientific notation card, where only the exponent moves.

3. Reading Eg as E-notation

In a calculator, 5e15 means 5 x 10^15. In a unit, Eg means exagram. The letters look alike but do different jobs.

4. Mixing Exa with Exbi

NIST SP 330 says SI prefixes are strict powers of 10. Exbi (Ei) is 2^60 and belongs to data sizes, not to mass.

5. Treating Rough Masses as Exact

A conversion keeps every digit, but an asteroid mass estimate is not known to 16 digits. Round to the precision of the source.

The Eg to kg conversion is exact. Any error comes from the source figure, its heading, or the rounding you choose afterward.

One exagram is exactly 1,000,000,000,000,000 kg, which is 10^15 kg.

There are 10^18 grams in an exagram, one quintillion grams.

One exagram is 10^12 metric tonnes, which is 1,000 gigatonnes. A tonne is 1,000 kg.

There are 1,000 Pg in 1 Eg, because exa is 1,000 times larger than peta.

Half an exagram is 500,000,000,000,000 kg, or 5 x 10^14 kg. It also equals 500 Pg.

Small moons and asteroids do. NASA lists Deimos at 2.4 x 10^15 kg, Eros at 6.69 x 10^15 kg and Phobos at 10.6 x 10^15 kg, which are 2.4, 6.69 and 10.6 Eg.

About 5,100 Eg. NASA gives the total mass of the atmosphere as 5.1 x 10^18 kg, and dividing by 10^15 gives 5,100.

The prefix symbol E is uppercase, like every multiple prefix from mega upward, and the gram symbol g is always lowercase.

Divide the kilograms by 10^15. For example, 1.06 x 10^16 kg is 10.6 Eg.

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• SI prefixes table, exa E = 10^18, with CGPM Resolution 10 (1975) for peta and exa (BIPM, International Bureau of Weights and Measures).
• Rule that mass prefixes attach to the gram, and that SI prefixes are strict powers of 10 (NIST SP 330, Section 3).
• Metric SI prefixes, with number names and the 1975 addition of peta and exa (NIST Office of Weights and Measures).
• Earth fact sheet: mass of Earth, atmosphere and hydrosphere (NASA Goddard Space Flight Center, last updated 15 November 2024).
• Asteroid fact sheet: masses in units of 10^15 kg, noted as rough estimates (NASA Goddard Space Flight Center). Phobos and Deimos are from the companion Mars fact sheet.