What trimmer length is a three-day stubble?

Between 1 and 2 mm — a thirty-second to a sixteenth of an inch — which is why the number of settings inside that band matters far more than the top of a trimmer’s advertised range.

The arithmetic agrees with the name. A beard grows about 0.3 to 0.5 mm (0.01 to 0.02 in) a day, so three days is 1 to 1.5 mm (0.04 to 0.06 in) of growth, and the look most people mean by a three-day stubble sits in that band or a touch above it. Growth rates differ between people, which is the honest caveat: a stubble is a length you choose and then keep, rather than a number of days you wait.

What decides whether a tool can hold it is the step size in that one narrow band. Counting the settings between 1 and 3 mm (0.12 in) on the trimmers here:

• the Braun BT9545, at 0.25 mm (0.01 in) per click, gives nine;
• the Braun BT5525, at 0.5 mm (0.02 in), gives five;
• the Remington MB5000 also steps 0.5 mm (0.02 in) at the short end, though Remington states “0.5 mm (0.02 in) to 2 mm (0.08 in) steps” across the range without saying where the step widens;
• the Philips OneBlade QP2824 has combs at 1, 3 and 5 mm (0.20 in), so it offers the two ends of the band and nothing between them.

That last line is the one to read twice. A trimmer advertised as 0.4–18 mm (0.02 to 0.71 in) and a trimmer with three stubble combs can both claim to cut a stubble; only one of them can move it by a hair.

The top of the range matters less than it looks — if a stubble is what you wear. Above about 6 mm (0.24 in), a quarter of an inch, the dial stops being a stubble control and becomes a beard control, and at that point the step size stops mattering because the eye cannot see half a millimeter in a beard that length. If you are growing a beard rather than holding a stubble, the useful part of the dial is the part this page treats as spare: see trimming a long beard.