Par time

Each level in Doom has an associated par time. After completing a level, the par time is displayed on the intermission screen next to the the time that the player took to complete the level. This allows the player to gauge their skill by comparing their time.

The par times are encoded into the Doom executable in the file. John Romero generated the par times by completing each level as fast as possible, rounding off the resulting time and adding 30 seconds.

Par times
The following are the par times from the Doom source code:

Doom

 * E1M1:30s
 * E1M2:1m15s
 * E1M3:2m
 * E1M4:1m30s
 * E1M5:2m45s
 * E1M6:3m
 * E1M7:3m
 * E1M8:30s
 * E1M9:2m45s
 * E2M1:1m30s
 * E2M2:1m30s
 * E2M3:1m30s
 * E2M4:2m
 * E2M5:1m30s
 * E2M6:6m
 * E2M7:4m
 * E2M8:30s
 * E2M9:2m50s
 * E3M1:1m30s
 * E3M2:45s
 * E3M3:1m30s
 * E3M4:2m30s
 * E3M5:1m30s
 * E3M6:1m30s
 * E3M7:2m45s
 * E3M8:30s
 * E3M9:2m15s
 * E4M12m45s
 * E4M24m15s
 * E4M32m15s
 * E4M42m30s
 * E4M53m
 * E4M66m30s
 * E4M72m15s
 * E4M86m
 * E4M93m

Doom II

 * MAP01: 30s
 * MAP02: 1m30s
 * MAP03: 2m
 * MAP04: 2m
 * MAP05: 1m30s
 * MAP06: 2m30s
 * MAP07: 2m
 * MAP08: 2m
 * MAP09: 4m30s
 * MAP10: 1m30s
 * MAP11: 3m30s
 * MAP12: 2m30s
 * MAP13: 2m30s
 * MAP14: 2m30s
 * MAP15: 3m30s
 * MAP16: 2m30s
 * MAP17: 7m
 * MAP18: 2m30s
 * MAP19: 3m30s
 * MAP20: 2m30s
 * MAP21: 4m
 * MAP22: 2m30s
 * MAP23: 3m
 * MAP24: 2m30s
 * MAP25: 2m30s
 * MAP26: 5m
 * MAP27: 5m30s
 * MAP28: 7m
 * MAP29: 5m
 * MAP30: 3m
 * MAP31: 2m
 * MAP32: 30s

User made maps
Due to the times being hardcoded into the executable, in the past it was often disregarded in custom PWADs. Until the advent of BEX, there was no way to set a time relating to the new levels that had been created (barring supplying a modified game binary). Advanced source ports allow the author to specify a par time using BEX or their own methods for this, so par times in custom levels are more common now.