How strong is earth's magnetic field?

Answer 1

Not very strong in comparison with a typical small "bar magnet" which has a field strength of roughly 100 gauss.

Earth's magnetic field strength at the surface is about 0.3 to 0.6 gauss.

That's stronger than some planets and weaker than others.

Answer 2

Magnetic Field Strengths are often measured in the unit "gauss" ( the SI unit is the "tesla"). The strength of the Earth's Magnetic Field, measured at its core, is 25 gauss.

More useful probably is the strength of the field at the surface of the Earth.

This varies from place to place. Also, it seems to have become weaker over recent centuries.

The strength at the surface is about 0.3 to 0.6 gauss.

(For comparison, a typical fridge magnet is about 50 gauss.)