In Roblox Lua, use string.format to convert 100 into 1.0 by dividing by 100 first:

lua

local num = 100
local result = string.format("%.1f", num / 100)
print(result) -- 1.0

If you want it as a number instead of text, keep the division:

lua

local result = 100 / 100
print(result) -- 1

A common pattern is:

  • 100 -> 1.0 with num / 100
  • 250 -> 2.5
  • 999 -> 9.9

If you meant turning 100 into the text "1.0" for a GUI label, the first example is the right one.