Customising your pacing card....
When I was a Trainee Mountain Leader, I did poor visibility / night navigation refresher with Paul Poole Mountaineering (would highly recommend this mountaineering guru and all-round good egg!). One of the things that was stressed was the room for error where arithmetic is concerned, especially when you're stressed, tired, hungry and would rather be in the pub.
If you have been on any mountain skills courses, you probably have a pacing card such as the one produced by Mountain Training (pictured). Customising your pacing card was something that Paul recommended...along with using beads / toggles to help you keep track of distance.
Paul also taught me the value of measuring distance on a map in millimetres to increase accuracy so having a quick way (without the maths) to work out how far 4mm is on a 1:25k map saves a lot of stress. I have also added some key messages on my card for the times when I need to calm myself and get back to basics with method and strategy. I hope you find this useful - please feel free to share.