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Brief description of geomagnetism and observation systems

About WMM

Learn more about model derivation, uncertainties and magnetic poles

Model & Software

Download model coefficients, software and documentation

Online Calculators

Calculate magnetic field values at or near the Earth surface


Browse imagery and contour maps for main field and secular change

Uses of WMM

Common applications of WMM


License and copyright information

The World Magnetic Model and Associated Software

This site provides access to the DoD software and current WMM model and WMM online calculator. The software computes the main components of the geomagnetic field and their annual changes. The programs are designed to be used in demand mode. The software is available as C source code. The model file, WMM.COF (format specification), is expected to reside in the same directory as the software. Note: The altitude is referenced to the World Geodetic System 1984 (WGS 84) ellipsoid. The WMM software library provides functions to convert height above mean sea level (AMSL) to height above WGS 84. This option is enabled by default.

Input And Output

The input parameters and valid entries are:

Latitude -90.00 to +90.00 degrees
Longitude -180.00 to +180.00 degrees
Altitude -1 to 850km referenced to the WGS 84 ellipsoid OR the Mean Sea Level (MSL)
Date 2020.0 to 2025.0

The seven magnetic components computed are:

F - Total Intensity of the geomagnetic field
H - Horizontal Intensity of the geomagnetic field
X - North Component of the geomagnetic field
Y - East Component of the geomagnetic field
Z - Vertical Component of the geomagnetic field
I (DIP) - Geomagnetic Inclination
D (DEC) - Geomagnetic Declination (Magnetic Variation)

Annual change (also known as Secular Variation or SV) in each of these magnetic components is also displayed. The annual change is computed by subtracting the main field values for the desired input date from main field values one year later. The output units are displayed using the abbreviations nT (nanoTesla), deg (degrees) and min (minutes) per year. The new WMM2020 software also outputs uncertainty for each component. The error is one standard deviation difference between a hypothetical measurement and model output. The uncertainty values have the same units as their corresponding components.

Third party software for World Magnetic Model

    Third party software is available here. Note: Neither the authors nor NCEI can provide any warranty or technical support for these programs.

Changes made to the WMM Code

As changes are made to the WMM code, the revised code will be posted. Check this site for change notices. The downloadable code is always the latest version.

Cite / Reference Data

For the model values, cite as:
NCEI Geomagnetic Modeling Team and British Geological Survey. 2019. World Magnetic Model 2020. NOAA National Centers for Environmental Information. doi: 10.25921/11v3-da71, 2020, [date accessed].

For the technical report, cite as:
Chulliat, A., W. Brown, P. Alken, C. Beggan, M. Nair, G. Cox, A. Woods, S. Macmillan, B. Meyer and M. Paniccia, The US/UK World Magnetic Model for 2020­-2025: Technical Report, National Centers for Environmental Information, NOAA, doi:10.25923/ytk1-yx35, 2020.

Download the World Magnetic Model - WMM2020 - software and documentation.

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WMM2020 coefficient file

Release Date

Product Description


December 2019

WMM2020 Coefficient file (WMM.COF) valid for 2020.0 - 2025.0, test values and instructions to update your software. A technical specification of the WMM.COF file format is given here.

WMM2020 Software + Windows GUI

Release Date

Product Description


December 2019

World Magnetic Model (WMM2020) with C software and executables for Windows environment.


December 2019

World Magnetic Model (WMM2020) with C software and executables for Linux environment.


December 2019

World Magnetic Model (WMM2020) with Stand-alone Graphical User Interface (GUI) for Windows.

WMM2020 Documentation

Release Date

Product Description


December 2021

Report assessing the performance of the WMM2020 and describing noteworthy changes in the Earth's main magnetic field since WMM2020 was released.


April 2020

World Magnetic Model (WMM2020) - Technical Report about the model development. For previous technical reports see old reports.


December 2019

World Magnetic Model (WMM2020) - Test values.


December 2019

World Magnetic Model (WMM2020) - ISO XML Metadata.

WMM2020 Mobile Apps

Release Date

Product Description


February 2019

World Magnetic Model Android software as part of "CrowdMag" app (uses the WMM2015v2 until the app review process is completed).


February 2019

World Magnetic Model iOS software as part of "CrowdMag" app (uses the WMM2015v2 until the app review process is completed).

WMM2020 Old Software

Release Date

Product Description


December 2019

Legacy Fortran software available with WMM2020 coefficients from our third party page.


December 2019

Legacy C software available with WMM2020 coefficients from our third party page.

Last Modified on: Tuesday, 04-Feb-2020 23:28:00 UTC
NOAA > NESDIS > NCEI (formerly NGDC)
Maintained by: geomag.models@noaa.gov