Here we explain the basics of how to measure for a typical pedestrian gate with side panel(s). Words in green can be clicked for further explanation. Don't forget we are here to help if you get stuck.
Remember if we are installing the gates for you there is no need to consider any of these points as they will be taken care by us.
In an ideal world posts and wall plates will be perfectly vertical and parallel to each other and while this should be possible with new posts it isn’t always the case with brickwork, old and new. The basic principle remains the same though.
The drawings below show:
Posts 
Gate(s) 
1) How to measure for a pedestrian gate and side panel
Measure the total opening width. From this deduct the post or wall plate sizes, the required gate size and the opening tolerances these will later be covered by gate stops. This will give you the side panel size.
Our examples uses two posts and wall plate .
Total opening width is 2400mm (2.4m) deduct 125mm for the left hand closing post, deduct 125mm for the hanging post and another 25mm for the total opening tolerance .
2400mm – 125mm - 900mm – 125mm - 25mm = 1225mm and this is your side panel length.
The photo and diagram show all of the components, as you can see the final wall plate used for the side panel is situated behind so cannot be seen from the front giving a neater finish which does not affect the length of the side panel when measuring. The same applies if you were using a post and typically this would be a smaller post
2) How to measure for a pedestrian gate with side panel either side.
Measure the total opening width. From this deduct the post or wall plate sizes, the required gate size and the opening tolerances these will later be covered by gate stops. Divide by 2 this will give you the equal side panel size of course you can just as easily have unequal side panels if that suits.
Our examples uses two posts and 2 wall plates .
Total opening width is 2400mm (2.4m) deduct 125mm for the hanging post and 125mm for the closing post , deduct 900mm for the gate and another 25mm for the total opening tolerance then divide by 2.
2400mm – 125mm - 125mm - 900mm - 25mm = 1225 / 2 = 612mm for the length of each side panel.
The photo and diagram show all of the components, as you can see the wall plates used for the side panels are situated behind so cannot be seen from the front giving a neater finish which does not affect the length of the side panel when measuring. The same applies if you were using a post and typically this would be a smaller post.