Concepts → Great Weapon Fighting vs raw rerolls

Great Weapon Fighting — does the reroll-on-1 actually buy you anything?

Great Weapon Fighting (GWF) lets you reroll any 1 or 2 on a damage die from a two-handed melee weapon. Players regularly ask: does that swing the math meaningfully, or is it a negligible buff that flavour-tax fighters pay for? The exact rationals are easier than you'd think — and the answer differs by weapon.

The GWF rule (and the engine's `r1` notation)

Per RAW: when you roll damage with a two-handed melee weapon you're proficient with, you can reroll any 1 or 2. The 2024 version uses the same trade. Diceplots' parser supports reroll-on-N via the rN suffix: 2d6r1+5 rerolls each die that came up 1 (matches RAW for 1-only rerolls); for the standard "1 or 2" reroll, use r2.

In every case below, "GWF" is shorthand for the more common reroll-on-1-or-2 variant; the math for reroll-on-1-only is almost identical, just smaller.

Greatsword — the headline weapon

Greatsword damage is 2d6+STR. Two dice means GWF's reroll fires roughly twice as often as on a single-die weapon.

2d6+5

min 7 max 17

7 2.78%
8 5.56%
9 8.33%
10 11.11%
11 13.89%
12 16.67%
13 13.89%
14 11.11%
15 8.33%
16 5.56%
17 2.78%

2d6r1+5

min 7 max 17

7 0.08%
8 1.08%
9 4.86%
10 8.64%
11 12.42%
12 16.20%
13 18.90%
14 15.12%
15 11.34%
16 7.56%
17 3.78%

Mean shifts:

E[2d6+5] = 12 — exact.
E[2d6r1+5] = 12 + 2·(1/6 · 0.5) = 12 + 1/6 ≈ 12.17 for reroll-on-1-only.
E[2d6r2+5] = 12 + 2·(2/6 · 1) = 12 + 2/3 ≈ 12.67 for reroll-on-1-or-2 (RAW GWF).

That ~5% mean increase compounds across a campaign — a Greatsword Fighter swinging twice per round at level 5 over a typical adventuring day adds up to noticeable damage. But it's not a big number per swing.

Greataxe — half the effect

Greataxe damage is 1d12+STR. One die, but a d12 — so the reroll fires less often per attack and the d12 has a wider tail to land in after a reroll.

1d12+5

min 6 max 17

6 8.33%
7 8.33%
8 8.33%
9 8.33%
10 8.33%
11 8.33%
12 8.33%
13 8.33%
14 8.33%
15 8.33%
16 8.33%
17 8.33%

1d12r1+5

min 6 max 17

6 0.69%
7 9.03%
8 9.03%
9 9.03%
10 9.03%
11 9.03%
12 9.03%
13 9.03%
14 9.03%
15 9.03%
16 9.03%
17 9.03%

Mean shifts:

E[1d12+5] = 11.5 — exact.
E[1d12r1+5] = 11.5 + 1/12 · 5.5 ≈ 11.96 for reroll-on-1-only. The 5.5 is the mean of the rerolled die.
E[1d12r2+5] = 11.5 + 2/12 · 5 ≈ 12.33 for reroll-on-1-or-2 (RAW GWF).

So GWF on a Greataxe gives a ~0.5 mean bump at +5 STR vs Greatsword's ~0.7 — a bit less, in absolute terms, despite the Greataxe's higher raw damage cap.

The variance angle — the surprising part

GWF cuts low rolls. It doesn't change high rolls. So the distribution gets narrower, not just shifted right. That has knock-on effects on kill probability:

Below the mean (target HP < your average swing), the higher-variance non-GWF roll wins more often than the narrower GWF roll, by a small margin — same logic as variance and kill probability. Counter-intuitive.
Around the mean, GWF is a strict win — it raises the floor without lowering the ceiling.
Well above the mean (one-shotting underleveled targets), the variance reduction is irrelevant — both rolls pulp the target.

So GWF is genuinely better mean DPR but the reduced variance means you'll see slightly fewer "miracle 24-damage crits" — because the reroll cuts the lows, the high tail becomes proportionally less impressive.

The takeaway

GWF is a real buff, not a flavour-tax. But the per-swing magnitude is small (roughly +0.5 to +0.7 mean damage on common weapons), and the variance reduction means it slightly hurts your kill probability in the regime where you're chip-damaging targets above your single-swing mean. In the regime where you're meeting or exceeding your mean, it's a strict improvement.

Stack-rank: pick GWF over Defense fighting style if you're DPR-focused and your typical target HP sits around or above your swing mean. Defense's flat +1 AC is more universally valuable and doesn't have the variance-reduction tradeoff — see the number at the back of any optimisation thread.

Try it yourself

↦ /vs/2d6+5/2d6r1+5 — Greatsword vs GWF Greatsword ↦ /vs/1d12+5/1d12r1+5 — Greataxe vs GWF Greataxe ↦ /strike/2d6r1+5 — full GWF Greatsword distribution

Drag the HP slider — at low HP (5-8), the non-GWF roll's higher variance gives it a slight edge; at HP near the mean (10-12), GWF takes over; well above, both reliably finish.