Timekeeper

Timekeeper is a simple and easy-to-use tick profiler data pack for Minecraft: Java Edition 1.19+. It measures the milliseconds per tick (MSPT) of the world/server you run it on.

Using it is very simple. Just type in /scoreboard players set $enabled timekeeper.var <insert number here>, and the datapack will keep track of the MSPT for however many ticks you specify. Once the time is done, it will print the average MSPT over the period to chat. (e.g. "Average MSPT over 50 ticks: 5")

If you want to continue profiling the tick rate indefinitely, you can use /scoreboard players set $enabled timekeeper.var -1, which will keep the bossbar up until told otherwise and thus will not print out a final average.

And that's all there is to it!