I got my last holdout hive under the treatment threshold today, which for me is 2%. With temperatures hovering around 38 degrees F today, the Mite Calculator came in extra handy. It was too cold to open the hive and collect a sample of bees, so it'd be tough otherwise to make an informed decision about whether I need to treat again next week.
If you've ever counted mites on a sticky board, you know it can be hard to keep track of what you've already counted. A few years ago I made this simple aid that helps with this problem. Counting one row at a time drastically improves the accuracy of the tally. Some sticky boards have a grid built into them, but for all others this is a handy tool.