Tesla vs Gauss: Magnetic Field Units Explained

How can the same magnet read 1.5 on one meter and 15,000 on another? Both numbers are correct. One meter reads in tesla and the other in gauss, and one tesla equals exactly 10,000 gauss. This guide shows what the two units measure, how to switch between them, and where real fields land.

Tesla and Gauss Side by Side

Every magnetic flux density unit has a fixed value in tesla. The table lists the six units our converter handles, plus the nanotesla that geophysicists use. Each row gives the same unit in tesla and in gauss.

Two pairs are worth memorizing. One millitesla equals 10 gauss, and one milligauss equals 0.1 microtesla. With those two links, most everyday conversions take only a moment.

Here are three quick practice conversions using the table. Each one moves between the families with a single multiply or divide.

Notice that the kilogauss sits close to the tesla. Ten kilogauss make exactly one tesla, so kG values read like tesla values with one extra zero. Our converter notes that kilogauss is used for moderately strong magnets and lab equipment.

A few terms show up in every magnet datasheet. Here is what each one means in plain words.

Magnetic flux density (B)

How concentrated a magnetic field is at one point. Tesla and gauss both measure B.

Tesla (T)

The SI unit of flux density, equal to one weber per square meter.

Gauss (G)

The older unit from the centimeter-gram-second system, equal to 0.0001 tesla.

Gamma

An older name for one nanotesla. NIST lists 1 gamma as exactly 0.000000001 tesla.

Field strength (H)

A related but different quantity, measured in amperes per meter or in oersteds.

What Do Tesla and Gauss Actually Measure?

Both units measure magnetic flux density, the strength of a magnetic field at a single point. The tesla belongs to the modern SI system. The gauss comes from the older centimeter-gram-second system.

The NIST guide to the SI defines the tesla as one weber per square meter. Picture magnetic field lines passing through a small window. Flux density tells you how tightly those lines crowd through each square meter.

This is different from total flux, measured in webers. Flux counts all the lines through a whole surface. Flux density divides that total by the area, which is why tesla equals webers per square meter.

Why do two units survive side by side? The tesla is huge for daily life, so small fields need awkward decimals. Gauss keeps weak fields in friendly whole numbers, much like psi and pascals coexist for pressure. Our guide to pressure units such as psi, bar and Pa shows the same pattern in a different field.

How Do You Convert Tesla to Gauss and Back?

Multiply tesla by 10,000 to get gauss. Divide gauss by 10,000 to get tesla. NIST lists the factor as 1 gauss = 0.0001 tesla, a fixed value that never drifts.

Our converter’s own example starts with 1 tesla. Multiply by 10,000, and the answer is 10,000 gauss. The same rule turns a 1.5 tesla scanner into 15,000 gauss.

Going the other way works just as cleanly. A 200 gauss magnet divided by 10,000 gives 0.02 tesla. Move the decimal three places, and that reads as 20 millitesla.

Prefixes cause more slips than the main factor. Remember that 1 gauss is 100 microtesla, not 1 microtesla. A reading of 50 uT is therefore 0.5 gauss, or 500 milligauss.

The magnetic field converter routes every value through tesla first. It multiplies by the source unit’s size in tesla, then divides by the target unit’s size.

How Strong Is the Earth’s Magnetic Field?

The Earth’s field ranges from about 25,000 to 65,000 nanotesla, according to NOAA’s geomagnetism team. That equals 25 to 65 microtesla, or 0.25 to 0.65 gauss.

The exact value depends on where you stand, so the top of the range is more than double the bottom. NOAA also reports that the north magnetic pole drifts about 55 km per year. Local readings slowly change as a result.

Survey scientists usually report the field in nanotesla. NOAA notes that 100,000 nanotesla make 1 gauss. A reading of 50,000 nT is therefore 50 uT, or half a gauss.

Our converter notes that environmental fields are often quoted in milligauss. The Earth’s range works out to 250 to 650 milligauss. That same span equals 0.025 to 0.065 millitesla, which shows why tesla feels clumsy at this scale.

How Many Gauss Is an MRI Scanner?

A 3 tesla MRI scanner produces 30,000 gauss, and a 7 tesla unit produces 70,000 gauss. The FDA says scanner strength is measured in tesla, written with the letter T.

According to the FDA, clinical scanners in the United States were 3 T and below until October 2017. That year the agency cleared the first 7 T system for clinical use. Its news release says higher field strength improves overall image quality.

Our converter’s example uses a 1.5 tesla scanner, which equals 15,000 gauss. Compared with Earth’s 50 uT, that is 30,000 times stronger. A 7 T magnet is 140,000 times stronger than the same Earth reading. In gauss, the jump runs from 0.5 G to 70,000 G.

Keep the unit math separate from safety questions. A scanner rated in tesla tells you its field strength, not what is safe to bring near it. Screening rules for each scan come from the imaging team.

Where Does Field Strength H Fit In?

Field strength H is a separate quantity from flux density B. H is measured in amperes per meter, while B uses tesla or gauss. Our converter handles B units only.

The two are linked through the material the field passes through. In a vacuum, B equals H times the magnetic constant. NIST lists that constant as about 0.0000012566 newtons per ampere squared.

Here is a quick check. An H of 1 ampere per meter in a vacuum gives about 1.2566 microtesla. Earth’s 50 uT, taken in air, matches an H of roughly 39.8 amperes per meter.

The older partner of H is the oersted. NIST lists 1 oersted as about 79.577 amperes per meter. In a vacuum or in air, 1 oersted of H produces 1 gauss of B, so the two numbers match.

Inside iron, that tidy match breaks down. The material changes how much B you get for the same H. For this reason, a datasheet in oersteds cannot be converted to gauss without knowing the material.

Questions People Ask About Tesla and Gauss

Where These Numbers Come From

This article covers unit conversion for magnetic flux density and is general science education. It does not give medical or MRI safety advice. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated September 27, 2026.