RogerBW's Blog

GURPS house rule: completion time 03 February 2017

This is a small extension of the GURPS rules to generate the time taken for tasks of variable length.

GURPS is generally quite fuzzy about how long it takes to do things, because there are plenty of external factors, but sometimes the exact amount of time matters. For those situations, we have the under-used Time Spent rules on p. B346: you know how long the task "should" take, you decide how long you want to take over it, and the difference gives you a penalty or bonus to your skill roll.

This house rule allows you to invert that for a situation in which you don't really care about degree of success or failure, but simply want to know how long it takes to do the job: can you get the lock picked before the bad guys come round the corner?

Make the skill roll without any modifiers for time spent. Take the margin of success, and convert that back to a duration using the Time Spent rules: pass by 5, and the job is done in half the time (i.e. the amount of time which would give you a -5 for haste). For tasks which can reliably be done eventually but may take a while, such as solving a puzzle, you can also use the margin of failure: miss the roll by 3, and you'll achieve the objective, but it'll take eight times as long as expected.

The main thing to watch out for here is that the task needs to be a binary one: "is the lock picked", "is the security pad bypassed". If you need margin of success for something else ("have I broken into this computer sneakily enough that I won't be noticed"), it can't also be used to generate time taken.

Tags: gurps rpgs

  1. Posted by John Dallman at 11:05am on 03 February 2017

    OK, that makes sense. The asymmetry in the time vs. skill progression for going faster or slower is part of the rules on B346. Critical failure presumably means you mess the job up in some way, and critical success that you find some really good way to do it?

  2. Posted by RogerBW at 11:42am on 03 February 2017

    I think the trick is to keep this to situations where quality of success really doesn't matter, so that one isn't tempted to overload the result. Meaningful results come between success by 9 (which will often be a critical too) and failure by 5 (which may well be a fumble, especially with task difficulties taken into account); I don't want to say that Mr Skill 10 jumps straight from success-by-5 to best-possible while Mr Skill 15 doesn't.

    Failure by more than 5 should count as failure at the task, I think.

    A cruel GM may wish to make the roll in secret, and not tell the player the duration.

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