Magnetic Field of a Straight Current-Carrying Wire Calculator

Your details

Choose which quantity to calculate. Provide the other two as inputs.
SI uses amperes, metres, and tesla. Practical uses amperes, centimetres, and millitesla.
Electric current flowing through the wire in amperes.
A
Perpendicular distance from the centre of the wire to the point where you want to know B.
m
Magnetic field (B)
0

Field strength at the specified distance from the wire

Magnetic field400.0000 nT
Compared to Earth's field0.01
Field directionUse the right-hand rule: curl your right-hand fingers around the wire with your thumb pointing in the current direction; your fingers indicate the field circulation direction.
0.01 x Earth B
Sub-geomagnetic<0.1Near Earth field0.1-110x Earth field1-10100x Earth field10+

At 5 m from a 10 A wire, B = 400.0000 nT

  • This field is about 125 times weaker than Earth's surface field. It would be difficult to measure without sensitive instrumentation.
  • Field strength falls off inversely with distance (1/r). Doubling the distance from the wire halves B; halving the distance doubles B.

Next stepTo reverse-solve - for example, to find the current needed to produce a given field at a known distance - switch the 'Solve for' selector to 'Current I'.

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