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How many base units does the International System of Units (SI) have?

Seven: meter, kilogram, second, ampere, kelvin, mole and candela.

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  1. 7 ✔
  2. 22
  3. 3

Why: The SI rests on 7 base units. Every other unit, like the newton or the volt, is built by multiplying and dividing those seven.

Huh, didn't know that: NIST counts 22 derived units with their own special names and symbols, from the hertz to the sievert.

The dad joke
Why did the meter, kilogram and second start a band? They were the base section.
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References

Answer: 7. The SI rests on 7 base units. Every other unit, like the newton or the volt, is built by multiplying and dividing those seven.

  1. NIST: SI Units www.nist.gov/pml/owm/metric-si/si-units
    The SI is made up of 7 base units that define the 22 derived units with special names and symbols
    Checked 2026-10-11.

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