Lambert 72 / Lambert 2008 ↔ WGS84

Convert between Lambert 72, Lambert 2008 and GPS

Enter coordinates in any one of the three systems and the other two are calculated at once. For longer lists switch to batch mode: one point per line, with spaces, commas, semicolons or tabs between the numbers, converted in either direction. Everything is calculated on your device, so a list of customer or property locations never leaves your browser.

The three Belgian coordinate systems

• Lambert 72 (Belgian Lambert 1972, EPSG:31370) – coordinates in metres on the Belgian Datum 1972 with the Hayford ellipsoid. It is still the most common system in Flemish and federal GIS data, cadastral plans and the address registers.
• Lambert 2008 (EPSG:3812) – the newer system on ETRS89, used by the NGI/IGN. Its numbers differ from Lambert 72 by roughly 500 km in both X and Y, so the two are easy to tell apart.
• WGS84 – the GPS latitude and longitude used by web maps and phones.

Worked example

The Grand-Place in Brussels is at about 50.8467° N, 4.3525° E in WGS84. In Lambert 72 that is roughly X 148 855 m, Y 170 700 m, and in Lambert 2008 roughly X 648 855 m, Y 670 700 m. The Lambert 2008 numbers are about 500 000 higher in each direction, which is a quick sanity check when you are unsure which system a file uses. Converting the Lambert 72 pair back returns the same GPS position within a fraction of a millimetre.

How accurate is it?

The datum conversion from BD72 to WGS84 uses the standard 7-parameter Helmert transformation (EPSG:15929). It is accurate to about one metre, which is fine for mapping and geocoding but not for surveying. For centimetre accuracy use the official grid-based transformations of the NGI.

Tips for working with Belgian coordinates

• X before Y. Lambert coordinates are written easting (X) first, then northing (Y). GPS is usually written latitude first, then longitude. Swapping them is the most common error.
• Check the range. A Lambert 72 point inside Belgium has an X of roughly 20 000 to 300 000 and a Y of roughly 20 000 to 250 000. Numbers around 650 000 point to Lambert 2008.
• Decimal separator. Use a point for decimals in batch lists, and separate the two numbers with a space, tab or semicolon.

Related tools

Convert whole GeoJSON or KML files with the GeoJSON and KML converter, measure areas and buffers with the geometry analyzer, look up the municipality and postcode of a place in the postcode and NIS lookup, and validate Flemish addresses with the address check.