EPSG:27700 — OSGB36 / British National Grid

Projected coordinate system · coordinates in metres · United Kingdom (UK) - offshore to boundary of UKCS within 49°45'N to 61°N and 9°W to 2°E; onshore Great Britain (England, Wales and Scotland). Isle of Man onshore.

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EPSG:27700OSGB36 / British National Grid

Coordinates in EPSG:4326 — one pair per line

Paste as many as you like: X,Y or X Y or X;Y (optional Z). Columns copied from Excel or a CSV work as-is.

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🔒 Runs entirely in your browser with GDAL WebAssembly — the same PROJ engine used by QGIS, PostGIS, and ArcGIS. Nothing is uploaded. Output units: metre.

Worked example — the centre of this system's area of use: -3.5, 55.38 (EPSG:4326 lon, lat) = 305,055.41, 610,582.45 (EPSG:27700).

EPSG:27700 is the British National Grid (OSGB36 / BNG) — the projected coordinate system used by Ordnance Survey and effectively all UK mapping, engineering, and government data. Coordinates are eastings and northings in metres, with the false origin placed southwest of the Isles of Scilly so every value on land is positive.

Its datum is OSGB36, not WGS 84 — so converting GPS coordinates into BNG involves a datum shift, not just a projection. This converter applies the standard OSGB36 ↔ WGS 84 transformation (about 2 m accuracy across Great Britain). Survey-grade work needs the Ordnance Survey OSTN15 grid, which refines results to centimetres.

EPSG:27700 details

TypeProjected CRS

DatumOrdnance Survey of Great Britain 1936

Unitsmetre

AxesEasting (east) · Northing (north)

Projection methodTransverse Mercator

ScopeEngineering survey, topographic mapping.

Base CRSEPSG:4277

Area of use

United Kingdom (UK) - offshore to boundary of UKCS within 49°45'N to 61°N and 9°W to 2°E; onshore Great Britain (England, Wales and Scotland). Isle of Man onshore.

WGS84 bounds: -9.01° to 2.01° longitude, 49.75° to 61.01° latitude.

Well-known text (WKT2)

Show WKT2 definition for EPSG:27700

PROJCRS["OSGB36 / British National Grid",BASEGEOGCRS["OSGB36",DATUM["Ordnance Survey of Great Britain 1936",ELLIPSOID["Airy 1830",6377563.396,299.3249646,LENGTHUNIT["metre",1]]],PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433]],ID["EPSG",4277]],CONVERSION["British National Grid",METHOD["Transverse Mercator",ID["EPSG",9807]],PARAMETER["Latitude of natural origin",49,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8801]],PARAMETER["Longitude of natural origin",-2,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8802]],PARAMETER["Scale factor at natural origin",0.9996012717,SCALEUNIT["unity",1],ID["EPSG",8805]],PARAMETER["False easting",400000,LENGTHUNIT["metre",1],ID["EPSG",8806]],PARAMETER["False northing",-100000,LENGTHUNIT["metre",1],ID["EPSG",8807]]],CS[Cartesian,2],AXIS["(E)",east,ORDER[1],LENGTHUNIT["metre",1]],AXIS["(N)",north,ORDER[2],LENGTHUNIT["metre",1]],USAGE[SCOPE["Engineering survey, topographic mapping."],AREA["United Kingdom (UK) - offshore to boundary of UKCS within 49°45'N to 61°N and 9°W to 2°E; onshore Great Britain (England, Wales and Scotland). Isle of Man onshore."],BBOX[49.75,-9.01,61.01,2.01]],ID["EPSG",27700]]

Frequently asked questions

How do I convert latitude/longitude to British National Grid?

Set the converter on this page to go from EPSG:4326 to EPSG:27700 and paste your longitude, latitude values. You will get easting and northing in metres. The transformation includes the OSGB36 datum shift (~2 m accuracy), which is why results differ by ~100 m from a naive Transverse Mercator formula that skips it. For centimetre-grade results, use Ordnance Survey tools with the OSTN15 grid.

What do British National Grid coordinates look like?

Six-digit eastings (0–700,000) and six- or seven-digit northings (0–1,300,000), in metres. Central London is around E 530,000, N 180,000. OS grid references such as TQ 30047 80422 are the same coordinates with the 100 km square encoded as two letters.

Should new UK data use EPSG:27700?

For anything that interacts with OS products, UK government data, or UK engineering workflows — yes, it remains the standard. For web display it is usually converted to EPSG:3857, and for GPS/data exchange to EPSG:4326. Store one, derive the others.