Rounding

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.
==See also==
*Grappling and Hit Location
*Targeted Attack
Category:Rules