Rounding is discussed on page 9 of GURPS Characters
- Round up in the positive direction for point costs ie -7.5 becomes -7 and 4.5 becomes 5
- Round down for character feats and combat results
- Except where instructed otherwise
- Exceptions and special cases (such as “round to the nearest whole number” or “do not round off”) are noted explicitly with the relevant rule
Special instructions include:
Rounding down[]
- pg 27 and 28, costs for Reputation are rounded down
- pg 52 ST is rounded down for "Weak" Extra Arms
- pg 55 "half move" is rounded down for Extra Legs
- pg 58 the fraction of Max ST available is rounded down
- pg 141 half basic speed for Crippled Legs is rounded down
- pg 142 1/4 ST is rounded down for wheelchair move
- pg 153 round down halved lifespan for Short Lifespan. This is seen in the chart with 25 becoming 12,
- pg 203 half of jumping skill for move for calculating distance
- pg 224 half of Symbol Drawing margin of success is rounded down for bonus
- pg 228 Zen Archery rounds down after multiplying penalties by 1/3
- pg 244 Rooted Feet rounds down halved dodge
- pg 247 damage from Explosive Fireball is rounded down after being divided by 3 for distance
Rounding up[]
- pg 36, costs of allies are rounded up (unlike reputation)
- pg 44 cost of Unreliable contacts rounds up
- pg 55 cost of Favor rounds up after fifthing cost
- pg 56 minimum speed for cannot hover
- pg 58 Gunslinger's halved accuracy bonus without aiming
- pg 59 cost of 1 FP per 2 HP healed
- pg 61 alternative attacks
- pg 76, the Complexity of a target of Digital possession must be half rounded up of the user's IQ. Unclear if it's possible for user to try and use a lower IQ.
- pg 83 Security Clearance cost
- pg 101 modifiers
- pg 108 Reduced Time
- pg 109 "1/2 HP per die of damage (round up);"
- pg 111 halved FP costs per minute
What UP means[]
There is some inconsistency about that. B9 initially mentions:
- For negative numbers, “up” means “in the positive direction”; e.g., if you multiply -7 points by 1/2 to get -3.5 points, round the result to -3 points
For example compare MA 68's right column of Targeted Attack;
- the fighter can buy off up to half of his default penalty (round up) for a strike
The examples given include:
- (Boxing Punch/Face): Defaults to Boxing-5; cannot exceed Boxing-2.
- (Broadsword Swing/Neck): Defaults to Broadsword-5; cannot exceed Broadsword-2
- TA (Judo Throw/Skull): Defaults to Judo-7; cannot exceed Judo-3.
This interprets "up" as being able to round 2.5 or 3.5 to 3 or 4 points bought off.
Now the left column:
- Grapples use half the usual hit location penalty:
- -3 for Face or Neck
B400 mentions you round penalties UP though:
- Halve hit location penalties (round up) if you are grappling a body part
TG5 though:
- The modifier can be improved up to the grappling penalty, but not more than that; e.g., when punching the skull, you could spend up to 4 CP to improve the hit location penalty from -7 to -3
TG7 though:
- If you are already grappling the head or torso, you may attack to grapple the neck at only -1 instead of -3
- The ear (Martial Arts, p. 137) is a pressure point, which can be grappled at -4
Necks are -5 and Ears are -7 normally, 2.5 and 3.5 halved appear to round "up" to 3 and 4.
So it is possible the -3 is a typo and intended to be -4 to punch the skull.
The "penalty" may be perceived as a positive number during halving before being subtracted from the to-hit skill.