LogFAQs > #944946555

Yes, its basically your chance to land a hit

lower is better as it states the minimum roll you need to have to hit an enemy whos AC is rated at 0

so, if your hero has a Thac0 of 10, and you swing at an enemy with AC 4, then you do 10-4 = 6, so you land a hit rolling 6 or higher (70% chance to hit)

if the same hero swings at an enemy with AC -2, then you do 10 + 2 = 12, so you have to roll 12 or higher (40% chance to hit)

Also a 1 always misses, and a 20 always hits, so the chance to hit is a maximum of 95%, and a minimum of 5%

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Posted from my iPhone 8