See whether the hem goes over the boot
With straight or wide trousers, try allowing the hem to fall over the boot shaft. Walk forward and turn. If the fabric catches, the opening may be too narrow for that boot or the length may land at an awkward point.
A cropped trouser can finish above the boot instead. Decide whether you like the visible gap and whether it suits the weather. You do not need to eliminate every gap, but you should not spend the day tugging the hem down to hide one.
Check the sole height
A trouser length chosen for flat shoes may sit differently over a heeled boot. Conversely, trousers altered for a heel can drag over a lower pair. Look at the back of the hem and walk on a clean, flat surface before deciding that the length is workable.
If you regularly wear one pair of trousers with two very different shoe heights, it may be easier to give that pair a primary job. Repeatedly improvising large cuffs is not always comfortable with a thick fabric.
Keep socks and fastenings in mind
Try the boots with the socks you intend to wear. A zip that closes comfortably over thin socks can feel restrictive over a thicker pair. Ensure fabric is clear of the zip rather than forcing the fastening.
Finish by sitting down, when trouser hems rise and show more of the boot. The combination should remain comfortable at the ankle. If it only looks right while you stand motionless, another trouser or boot shape may be more useful.
