Manual weighing of food is a widely used method for measuring rodent food intake, involving weighing a food dish before and after a feeding period. It is inexpensive, easily scalable to many cages, compatible with standard vivarium housing, and flexible across different diets, including the option to offer multiple foods simultaneously. However, weighing food accurately is not trivial!

Mice eat ~2-4g of food per day so if your method is returning values way above or below that, consider that your weights are likely not accurate. Some failure modes include:

• Using different weighing scales - different scales (even the same model) can be off by ~1g, so if you swap scales between days you will add noise here.
• Check that the scale is tared to 0 between each weighing - if the scale tare "drifts" during your weighing it will introduce systematic errors.
• Scales can be inaccurate if placed in a hood with the air on. Turn the air off while weighing.
• The scale can sometimes touch something like a notebook, giving an improper reading. Make sure there is nothing nudged up against the scale while weighing.
• Use weighing dishes with a metal grid to stop mice from taking large chunks out of the dish. While nothing is perfect, this is the best we've found, and is more accurate that dishes without grids, or weighing food from the wire rack on top.
• Accuracy can be compromised by food spillage and crumbs, as well as contamination from feces and urine in the food dish. Do your best to minimize or document these issues.

The best way to deal with all of this is to enter weights into a Google Drive sheet (Chantelle: Template sheet here!) as you weigh them, and use formulas to calculate the food eaten as you weigh them - if you get numbers that don't make sense (as in yellow below), you can re-weigh the food right away, or make a note of it if the weighing seems accurate but not plausible.