Technical Drawing Standards: Grid Reference Frame.

The typical ‘Engineering’ style drawing border has a grid reference frame drawn into the border. The grid references are used for the location and coordination of details.

Grid Line Weights

The Grid lines themselves are drawn with a 0.35mm line weight. They are spaced 50mm apart from the centring lines. The last two divisions can be whatever size they end up.

Grid References

The grid references start from the top left of the sheet, with letters running vertically from the top down and numbers running horizontally from left to right. On an A4 sheet the grids only need to be drawn on the top and left hand side. The letters I and O are not used – because they could be confused with 1 and 0.

BS ISO Grid Reference Frame

A3 Drawing Border with Grids – Click to enlarge

BS ISO Grid Reference Frame Enlarged Detail


The Number of Divisions depends on the Size of the Paper

Paper Size A0 A1 A2 A3 A4
Long Side 24 16 12 8 6
Short Side 16 12 8 6 4

BS EN ISO 5457:1999+A1:2010 Technical product documentation. Sizes and layout of drawing sheets

17 Responses to “Technical Drawing Standards: Grid Reference Frame.

  • Pratik
    9 years ago

    Hello Paul,
    Can you please guide me as to how I can go about setting up a grid reference on my drawing layout in paper space?. I am using AutoCad 2016. Thank you

  • Arturo Martinez
    9 years ago

    Thanks Paul, very useful info posted here

  • Paul,

    With regards to the exclusion of I and O from gridline lettering, is this a requirement of a particular BS, or is it just construction drawing folklore?

    We’re having debates in our office and I can’t find reference in any British Standard (yet)…


    • Hi Brent,

      I and O are specifically mentioned in the BS/ISO standard – Shall NOT be used ;)


  • Paul,
    That is all boxed up in ASME Y14.1 (M), and I don’t have a copy. I do know that most references I see (and that refer to ASME Y14.1) are established starting from (A1) the lower right corner, at the border. This way all sheets emanate from a common point.
    Sorry I can’t be of more assistance.

  • Don C.
    9 years ago

    Paul —

    Thanks, that’s what I needed.

    Don C.

  • Don C.
    9 years ago

    Paul —

    On page

    Is there a specification for the size of the reference field letters and numbers? Also for the distance between the grid frame and the drawing frame?

    If there is a spec, do these sizes depend on the paper size?

    Don C.

    • Hi Don,

      The size of the letters/Numbers is 3.5mm. The offset between drawing frame and grid border is 5mm.

      These dimensions are constant – only the number of fields changes with the paper size.

      Does that help?


  • Hi Lambertus,

    Not according to BS EN ISO 5457:1999. Do you have a copy?


    • Useful info Paul, thank you

      What does the BS EN ISO 5457:1999 say about calling out a Grid Reference: is it G14 or 14G – or personal preference??

      • Hi Matthew, that’s a good question!

        It doesn’t address your question directly:

        ‘The individual fields should be referenced from the top downwards… and from left to right’

        So I would go with ‘G14’ – unless anyone is aware of another convention?

        Does that help?


    • Kristy Moir
      9 years ago

      Interesting question from Lambertus – this seems strange to me, as typically if you are dealing with maps or graphs the reference is taken with 0,0 at the bottom left. I have seen it done both ways in drawing templates though.

      Does anyone have any knowledge on the logic behind this, or how this compares with ISO? Unfortunately I don’t have access to the BS or ISO at the moment.


  • Hi Paul shouldn’t the numbers be counted from right to left and the letters from down to up?