Compute the estimated values of Earth's magnetic field, including magnetic declination (D), based on the current World Magnetic Model (WMM), World Magnetic Model High Resolution (WMMHR) , or the International Geomagnetic Reference Field (IGRF) model. For 1590 to 1900 the calculator is based on the gufm1 model. A smooth transition from gufm1 to IGRF was imposed from 1890 to 1900. The calculator provides an easy way for you to get results in XML, CSV, or JSON programmatically (API). Registration is required to access this service. Please register using the API registration link on the top right.