Editing Warhammer 40,000/9th Edition Tactics (section)

====Wounding====
Instead of requiring a fixed roll, like hit rolls, most wound rolls (WR) instead require that you compare the Strength of the weapon to the target's Toughness, although some weapons do require a fixed roll. 

Your wound roll (R) is 2+ if S ≥ 2T, 3+ if 2T > S > T, 4+ if S = T, 6+ if S ≤ T/2, and 5+ if T/2 < S < T.

The odds of wounding (oow) with a modifier to wound <math>m</math> are 
<math display=block>\begin{align}
oow &= \frac{\min\left(6,\max\left(1,7-R+m\right)\right)}{6}\\
    &= \frac{\min\left(5,\max\left(1,m + 3 + \left\lceil\log_{2}{S}-\log_{2}{T}\right\rceil + \left\lfloor\log_{2}{S}-\log_{2}{T}\right\rfloor\right)\right)}{6}
\end{align}</math>

This means S and T scale with twice the base 2 logarithm of their values, subject to the wounding caps on either end of always failing on 1 and always succeeding on 6 - for example, S8 results in a 3 in the formula twice (which will always be close to having added 6), while S4 results in a 2 twice (always close to +4).  If you were to pay for Strength on a linear scale - 1 point for S1, 2 for S2, and so on - the most cost-effective S would be 3, because it adds about 3.17 to your wound formula, and is the only S for which you add more than S to the formula.  This also means doubling your S (as many melee weapons do) is usually as good as adding +2 to the formula, but adding to your S directly (as most of them do) has very diminishing returns.

*An ability to re-roll will multiply this value by (6+x)/6, where x is the number of facings on a wound roll you can re-roll, so if you re-roll 1s x is 1, re-roll 1s, 2s, 3s and 4s x is 4.
**For re-rolling 1s, x is always 1, and so the multiplier is always 7/6.
**For re-rolling ''failures'', x is larger the more likely you are to fail; a WR of 6+ multiplies by 11/6, 5+ by 10/6, and so on down to 2+ multiplying by 7/6.  Remember, re-rolling occurs before modifiers, which is one reason why re-rolling wounds is better than re-rolling failed wounds - you can re-roll "successes" that will be failures after a modifier.
*In practice, T will usually vary between 3 and 8 - T2, T9, T1, and T10 are all very rare, and you can just assume absolutely no targets have T11+.  As S values increase, this results in diminishing returns, as the weapon becomes better at wounding T values it will never encounter.  This is generally most obvious when considering S6->S7, which is ''only'' useful against T6 and T7 in practice.