Want to convert a grid reference to a tetrad code? Type your four figure grid refence (e.g. TG1748) or six figure grid reference (e.g. SK738911) into the box, press the Calculate button, and read off the displayed answer. (Note, for Irish grid references, be sure to add a prefix 'I' (e.g. IH2378).

Use the simple form (right) to select the tetrad of interest. Press the button to be taken to the Ordnance Survey Get-a-Map facility with a window showing just the tetrad you specified. Maps are currently only available for Britain. You can save or print the map using your browser.

If you are an online Atlas user, login to see lists of species and their breeding status in the squares where you have submitted records. If not already an online Atlas user, click here to go to the registration pages and make the most of the facilities there.