40 CARROTWhat is a unit's threat range in Warhammer 40K?
A unit's threat range is how far it can reach this turn: its Movement characteristic on its own, or its Movement plus a maximum 12" charge if it means to fight. A unit with 6" Movement threatens ground out to 6" — and melee out to 18" on a perfect charge roll. Everything beyond that line is safe from it this turn.
How do you calculate threat range?
Two numbers cover it. For a unit that just wants to be somewhere — an objective, a screen, a firing position — the threat range is simply its M characteristic. For a unit that wants a fight, add the charge: a charge roll can carry a unit at most 12 inches, so M + 12" is the outer edge of its melee threat. That maximum is the number that matters for safety math, because "probably won't make a 10-inch charge" and "cannot reach me" are very different plans. Playing to the true maximum — rather than the average roll — is what keeps units alive against fast melee armies: if you're 13" from a 6"-Move unit's front model, no roll in the game gets it to you.
How do you use threat ranges in a real game?
Threat range is the grammar of movement. Staging a unit means keeping it one inch outside the enemy's M+12" bubble while keeping the enemy inside yours; screening means placing cheap models so a charger physically can't end its move where it wants; baiting means offering a target just inside a bubble you want your opponent to commit into. All of it depends on reading distances accurately, which is tedious with a tape measure and free on a virtual table: 40 Carrot's threat range overlay (M / M+C) draws both rings around any unit, so you can see every bubble on the board at once and practice the positioning game until the distances become instinct.