Maidenhead Grid Locator
Convert lat/lng to Maidenhead grid codes (and back) for ham radio and contest work.
By Aryan Khan, Founder & Editor · Updated October 2026
For example, Times Square sits in locator FN30as, and London in IO91wm — six characters that ham operators exchange instead of addresses, precise to about 5 × 4 km.
How to use Maidenhead Grid Locator
The grid the world's radio amateurs navigate by:
The Maidenhead Grid Locator converts between latitude/longitude and Maidenhead locator squares — the hierarchical grid amateur radio uses to exchange locations. Enter a point and read its locator, from the 2-letter field down to the 6-character subsquare, or reverse a locator to the square it names.
- 1Enter coordinates or a grid code.
- 2Read the converted form.
What people use Maidenhead Grid Locator for
1. Ham radio operation
Contests and awards (VUCC, grid chasing) run on locators. Know yours before the pileup asks — and the station you worked gets logged by square, not by town.
2. VHF and microwave planning
On the high bands, contacts are grid-to-grid achievements. The locator frames what 'far' means when the band opens.
3. Decoding callsign lookups
QRZ pages and logs speak locators. The converter translates them into the geography the rest of this site uses.
4. Grid expeditions
Rare squares are destinations ('gridpeditions'). Find which square a summit or island activates before the drive.
Worked examples
FN is the field (20° × 10°), 30 the square (2° × 1°), 'as' the subsquare (~5.0 × 4.2 km at that latitude). Each pair refines by ten or twenty-four — the hierarchy in one string.
The world's most exchanged locator family starts IO91 — the square containing London. Operators who have never visited can place it instantly, which is the system's entire magic.
The locator hierarchy
Pairs of characters, each zooming further.
| Pair | Name | Cell size |
|---|---|---|
| 1st (letters A–R) | Field | 20° lon × 10° lat |
| 2nd (digits) | Square | 2° × 1° |
| 3rd (letters a–x) | Subsquare | 5′ × 2.5′ (~6 × 4 km at mid-latitudes) |
| 4th (digits) | Extended square | 30″ × 15″ — contest-grade precision |
The system divides the globe into 324 two-letter fields; each field contains 100 four-character squares.
Maidenhead locators describe radio grid squares, not street-level positions
The Maidenhead Locator System compresses latitude and longitude into an alphanumeric grid reference widely used in amateur radio. Short locators describe large areas; adding more characters narrows the square. That makes the system convenient for contacts, contests, antenna direction and logging without exchanging a full coordinate pair.
A locator is still an area reference rather than proof of an exact transmitter position. Keep the original GPS coordinate when precision matters, and do not confuse Maidenhead with MGRS, Plus Codes or geohash—each system has a different grid design and typical use case.
How to interpret the result
The most common errors come from using a correct result to answer the wrong geographic question. Keep these points in mind for Maidenhead Grid Locator:
- Adopt one storage format — decimal degrees, WGS84, five or six decimals — for every dataset you own, and convert at the edges for display. Mixed notations in one column are the root of nearly every coordinate bug.
- Sanity-check every pasted pair by eye on a map before using it: latitude/longitude swaps land you in the ocean so reliably that 'the Null Island bug' has a name. A two-second visual check costs nothing and catches most transcription errors.
Limits & appropriate use
Coordinates are lossless in principle and lossy in practice, and every loss is human: swapped axes, wrong hemispheres, datum relics, precision theatre. The converters eliminate the notation problem completely — DMS, UTM, MGRS and Plus Codes are exact translations on WGS84 — but they cannot eliminate the provenance problem: a number without its datum and its source is a rumour. Old NAD27-era documents, hand-typed sheets and seven-decimal CSVs each carry their own failure signature, and the honest tool answers with validation errors and visible pins rather than silent corrections.
The practical boundary is therefore organisational, not mathematical: teams that standardise storage (decimal, WGS84, sane precision) and ritualise the map check enjoy a lossless system; teams that don't accumulate expensive folklore. For work beyond consumer frames — control points, machine guidance, legal description — the escalation is geodetic: licensed surveyors, published transformations and national datums. Everything between a pasted waypoint and that door is exactly where this toolset lives.
- Datum-critical legacy data → published grid transformations (NTv2/HTDP).
- Control points and machine guidance → licensed geodetic survey.
- Aviation/marine charts → the chart's own datum and notation, verbatim.
Data & methodology
The locator divides longitude and latitude into successive fields, squares, subsquares and extended squares. Decoding returns the cell bounds and centre, not an exact station position. Coordinates are interpreted as decimal latitude and longitude.
For source details, licences and model limitations, see Data Sources and Methodology.
Key terms worth knowing
- UTM
- Metre-based zone/easting/northing grid on the WGS84 ellipsoid.
- Plus Code
- Open Location Code: keyless short codes for any spot, by open math.
Editorial guidance: MapBench explains the method and limitations so the tool can be used as a transparent reference, not as a black-box answer. For legal boundaries, safety-critical routing, surveying, engineering, regulated decisions or official statistics, verify the result with the responsible authority or a qualified professional.
Category: Coordinates. Results are intended for everyday analysis and planning unless a page explicitly states otherwise.
Method, assumptions & limits
- This tool’s method
- The locator divides longitude and latitude into successive fields, squares, subsquares and extended squares. Decoding returns the cell bounds and centre, not an exact station position. Coordinates are interpreted as decimal latitude and longitude.
- Before relying on the answer
- Record the coordinate order, signs, format and datum where specified. In GeoJSON, positions are longitude first; many input forms ask for latitude first.
- What the result cannot establish
- A format conversion preserves the source measurement's uncertainty. Extra digits do not improve the original GPS fix.
Coverage: Worldwide. Search, basemap and external data requests may use third-party services; browser-based does not mean every operation is offline. Read the source and licence notes, calculation methodology and privacy policy. If a result looks inconsistent, report a correction with the inputs and mode used.
Frequently asked questions
Clear answers about the calculation, accuracy and appropriate use.
Precision?
Longer locators are finer squares — match length to your needs.
Which datum do these coordinate tools use?
MapBench location tools generally use WGS84 latitude and longitude, the same global reference system commonly used by GPS and web maps.
Do more decimal places always mean better accuracy?
No. More digits increase numeric precision, but they cannot improve the accuracy of the original GPS, survey or source data.
Can I copy the result into GIS software?
Usually yes. Check the format, axis order and datum expected by the destination software before importing.
What does this tool calculate?
The Maidenhead locator for a coordinate pair (to subsquare or extended precision), and the square's location for a locator — the standard IARU system.
Do I need an account?
No — coordinates or locator in, answer out; no callsign required either.
Can I use the result for professional work?
For amateur radio, awards and planning it is the standard itself. Professional surveying uses other frames, as everywhere.
Case matters?
Convention: field and subsquare letters as given (fields uppercase, subsquares usually lowercase) — parsers are case-tolerant, humans are traditionalists.
Ocean squares?
Every point on Earth has a locator, sea included — maritime mobiles exchange them like everyone else.
My square straddles a border.
Most do — the grid ignores politics completely, which operators consider a feature.
Extended precision beyond 6 characters?
The 8-character extended square (~700 × 500 m) serves microwave work; the hierarchy continues by the same alternating pattern.
Antipodes?
Every square has one; DXers plan around the antipode's greyline like sailors around weather.
Related tools and resources
Other grids: the Geohash Encoder and MGRS Converter; centres: the Geographic Center Finder; your square: Find My Location.
More free tools
Sources, methodology & editorial trust
- ✓ Browser-first processing where supported
- ✓ External sources are documented
- ✓ No account required for public tools
- ✓ Review data sources
Calculations are documented with their assumptions, limitations and source context rather than presented as unexplained answers.
Reviewed and maintained by Aryan Khan, Founder & Editor of MapBench.
Part of our coordinates hub
Maidenhead Grid Locator sits in the coordinates cluster, alongside 63 other tools that answer neighbouring questions with different methods or datasets.
You may also need
When this answer is only part of the job, these clusters cover the next step.
Read the guide behind this tool
Understanding GPS Coordinates: Formats, Datums and Precision — A practical guide to latitude/longitude: what decimal degrees and DMS really mean, why datums matter, and how many decimal places you actually need.