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1
2
If a cell has red text, it means: your average damage per attack (DPA) with GWM is less than your average DPA without.
If a cell is highlighted in red, it means: you can't hit at all with GWM.

Note: The "Hit On" column is the value you would need to roll on a d20, before modifiers, to hit without GWM. When using GWM, your actual roll needed to hit is 5 higher.

Additional note: A typical two-handed weapon, like a greatsword, will deal somewhere between 2d6+2 and 2d6+8, depending on your Str and enchantments.
If we assume a Str of 20 and no enchants, average damage is 12.

So if you're average and hitting on a 9+ or better (or 11+ or better and have advantage), use your GWM. (Unless you can already kill the target in one hit.)
The relevant cell is outlined in sky blue.
3
4
5
6
7
8
9
10
11
DPA increase from Great Weapon Master, without advantage
12
hit on \ dmg
12345678910111213141516171819202122232425262728293031
13
26.756.506.256.005.755.505.255.004.754.504.254.003.753.503.253.002.752.502.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75
14
36.256.005.755.505.255.004.754.504.254.003.753.503.253.002.752.502.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25
15
45.755.505.255.004.754.504.254.003.753.503.253.002.752.502.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75
16
55.255.004.754.504.254.003.753.503.253.002.752.502.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25
17
64.754.504.254.003.753.503.253.002.752.502.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75
18
74.254.003.753.503.253.002.752.502.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25
19
83.753.503.253.002.752.502.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75
20
93.253.002.752.502.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25
21
102.752.502.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75
22
112.252.001.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25
23
121.751.501.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25-5.50-5.75
24
131.251.000.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25-5.50-5.75-6.00-6.25
25
140.750.500.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25-5.50-5.75-6.00-6.25-6.50-6.75
26
150.250.00-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25-5.50-5.75-6.00-6.25-6.50-6.75-7.00-7.25
27
16-0.25-0.50-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25-5.50-5.75-6.00-6.25-6.50-6.75-7.00-7.25-7.50-7.75
28
17-0.75-1.00-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25-5.50-5.75-6.00-6.25-6.50-6.75-7.00-7.25-7.50-7.75-8.00-8.25
29
18-1.25-1.50-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25-5.50-5.75-6.00-6.25-6.50-6.75-7.00-7.25-7.50-7.75-8.00-8.25-8.50-8.75
30
19-1.75-2.00-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25-5.50-5.75-6.00-6.25-6.50-6.75-7.00-7.25-7.50-7.75-8.00-8.25-8.50-8.75-9.00-9.25
31
20-2.25-2.50-2.75-3.00-3.25-3.50-3.75-4.00-4.25-4.50-4.75-5.00-5.25-5.50-5.75-6.00-6.25-6.50-6.75-7.00-7.25-7.50-7.75-8.00-8.25-8.50-8.75-9.00-9.25-9.50-9.75
32
33
34
DPA increase from Great Weapon Master, with advantage
35
hit on \ dmg
12345678910111213141516171819202122232425262728293031
36
29.018.938.848.758.668.588.498.408.318.238.148.057.967.887.797.707.617.537.447.357.267.187.097.006.916.836.746.656.566.486.39
37
38.668.558.448.338.218.107.997.887.767.657.547.437.317.207.096.986.866.756.646.536.416.306.196.085.965.855.745.635.515.405.29
38
48.268.137.997.857.717.587.447.307.167.036.896.756.616.486.346.206.065.935.795.655.515.385.245.104.964.834.694.554.414.284.14
39
57.817.657.497.337.167.006.846.686.516.356.196.035.865.705.545.385.215.054.894.734.564.404.244.083.913.753.593.433.263.102.94
40
67.317.136.946.756.566.386.196.005.815.635.445.255.064.884.694.504.314.133.943.753.563.383.193.002.812.632.442.252.061.881.69
41
76.766.556.346.135.915.705.495.285.064.854.644.434.214.003.793.583.363.152.942.732.512.302.091.881.661.451.241.030.810.600.39
42
86.165.935.695.455.214.984.744.504.264.033.793.553.313.082.842.602.362.131.891.651.411.180.940.700.460.22-0.01-0.25-0.49-0.72-0.96
43
95.515.254.994.734.464.203.943.683.413.152.892.632.362.101.841.581.311.050.790.520.260.00-0.26-0.52-0.79-1.05-1.31-1.58-1.84-2.10-2.36
44
104.814.534.243.953.663.383.092.802.512.231.941.651.361.080.790.500.21-0.08-0.36-0.65-0.94-1.23-1.51-1.80-2.09-2.38-2.66-2.95-3.24-3.53-3.81
45
114.063.753.443.132.812.502.191.881.561.250.940.630.310.00-0.31-0.63-0.94-1.25-1.56-1.88-2.19-2.50-2.81-3.13-3.44-3.75-4.06-4.38-4.69-5.00-5.31
46
123.262.932.592.251.911.581.240.900.560.23-0.11-0.45-0.79-1.13-1.46-1.80-2.14-2.48-2.81-3.15-3.49-3.83-4.16-4.50-4.84-5.18-5.51-5.85-6.19-6.53-6.86
47
132.412.051.691.330.960.600.24-0.13-0.49-0.85-1.21-1.58-1.94-2.30-2.66-3.03-3.39-3.75-4.11-4.48-4.84-5.20-5.56-5.93-6.29-6.65-7.01-7.38-7.74-8.10-8.46
48
141.511.130.740.35-0.04-0.43-0.81-1.20-1.59-1.98-2.36-2.75-3.14-3.53-3.91-4.30-4.69-5.08-5.46-5.85-6.24-6.63-7.01-7.40-7.79-8.18-8.56-8.95-9.34-9.73-10.11
49
150.560.15-0.26-0.68-1.09-1.50-1.91-2.33-2.74-3.15-3.56-3.98-4.39-4.80-5.21-5.63-6.04-6.45-6.86-7.28-7.69-8.10-8.51-8.93-9.34-9.75-10.16-10.58-10.99-11.40-11.81
50
16-0.44-0.88-1.31-1.75-2.19-2.63-3.06-3.50-3.94-4.38-4.81-5.25-5.69-6.13-6.56-7.00-7.44-7.88-8.31-8.75-9.19-9.63-10.06-10.50-10.94-11.38-11.81-12.25-12.69-13.13-13.56
51
17-1.49-1.95-2.41-2.88-3.34-3.80-4.26-4.73-5.19-5.65-6.11-6.58-7.04-7.50-7.96-8.43-8.89-9.35-9.81-10.28-10.74-11.20-11.66-12.13-12.59-13.05-13.51-13.98-14.44-14.90-15.36
52
18-2.59-3.08-3.56-4.05-4.54-5.03-5.51-6.00-6.49-6.98-7.46-7.95-8.44-8.93-9.41-9.90-10.39-10.88-11.36-11.85-12.34-12.83-13.31-13.80-14.29-14.78-15.26-15.75-16.24-16.73-17.21
53
19-3.74-4.25-4.76-5.28-5.79-6.30-6.81-7.33-7.84-8.35-8.86-9.38-9.89-10.40-10.91-11.43-11.94-12.45-12.96-13.48-13.99-14.50-15.01-15.53-16.04-16.55-17.06-17.58-18.09-18.60-19.11
54
20-4.94-5.48-6.01-6.55-7.09-7.63-8.16-8.70-9.24-9.78-10.31-10.85-11.39-11.93-12.46-13.00-13.54-14.08-14.61-15.15-15.69-16.23-16.76-17.30-17.84-18.38-18.91-19.45-19.99-20.53-21.06
55
56
57
DPA increase from Great Weapon Master, with Elven Accuracy
58
hit on \ dmg
12345678910111213141516171819202122232425262728293031
59
29.709.689.659.629.609.579.549.529.499.469.439.419.389.359.339.309.279.259.229.199.179.149.119.099.069.039.008.988.958.928.90
60
39.539.499.459.409.369.329.289.249.199.159.119.079.038.998.948.908.868.828.788.738.698.658.618.578.528.488.448.408.368.328.27
61
49.309.249.189.129.069.008.948.888.818.758.698.638.578.518.458.398.338.278.218.158.098.037.977.917.847.787.727.667.607.547.48
62
59.018.928.848.768.678.598.518.428.348.268.178.098.017.937.847.767.687.597.517.437.347.267.187.097.016.936.846.766.686.606.51
63
68.648.538.428.318.208.097.987.887.777.667.557.447.337.227.117.006.896.786.676.566.456.346.236.136.025.915.805.695.585.475.36
64
78.208.067.927.787.647.507.367.227.086.946.806.666.526.396.256.115.975.835.695.555.415.275.134.994.854.714.574.434.294.164.02
65
87.677.497.327.156.976.806.636.466.286.115.945.765.595.425.245.074.904.724.554.384.204.033.863.693.513.343.172.992.822.652.47
66
97.046.836.626.416.205.995.785.575.365.154.944.734.524.314.093.883.673.463.253.042.832.622.412.201.991.781.571.361.150.940.72
67
106.326.075.815.565.315.064.814.564.304.053.803.553.303.042.792.542.292.041.781.531.281.030.780.530.270.02-0.23-0.48-0.73-0.99-1.24
68
115.485.194.894.594.304.003.703.413.112.812.522.221.921.631.331.030.730.440.14-0.16-0.45-0.75-1.05-1.34-1.64-1.94-2.23-2.53-2.83-3.13-3.42
69
124.534.193.843.503.152.812.462.121.771.421.080.730.390.04-0.30-0.65-1.00-1.34-1.69-2.03-2.38-2.72-3.07-3.42-3.76-4.11-4.45-4.80-5.14-5.49-5.83
70
133.463.062.662.271.871.471.070.670.28-0.12-0.52-0.92-1.32-1.72-2.11-2.51-2.91-3.31-3.71-4.10-4.50-4.90-5.30-5.70-6.09-6.49-6.89-7.29-7.69-8.09-8.48
71
142.261.801.350.890.44-0.02-0.47-0.93-1.38-1.83-2.29-2.74-3.20-3.65-4.11-4.56-5.01-5.47-5.92-6.38-6.83-7.29-7.74-8.20-8.65-9.10-9.56-10.01-10.47-10.92-11.38
72
150.910.40-0.12-0.63-1.15-1.66-2.17-2.69-3.20-3.72-4.23-4.75-5.26-5.78-6.29-6.80-7.32-7.83-8.35-8.86-9.38-9.89-10.40-10.92-11.43-11.95-12.46-12.98-13.49-14.01-14.52
73
16-0.58-1.16-1.73-2.31-2.89-3.47-4.05-4.63-5.20-5.78-6.36-6.94-7.52-8.09-8.67-9.25-9.83-10.41-10.98-11.56-12.14-12.72-13.30-13.88-14.45-15.03-15.61-16.19-16.77-17.34-17.92
74
17-2.22-2.87-3.51-4.16-4.80-5.45-6.10-6.74-7.39-8.03-8.68-9.32-9.97-10.62-11.26-11.91-12.55-13.20-13.84-14.49-15.13-15.78-16.43-17.07-17.72-18.36-19.01-19.65-20.30-20.95-21.59
75
18-4.03-4.74-5.46-6.18-6.89-7.61-8.33-9.05-9.76-10.48-11.20-11.91-12.63-13.35-14.06-14.78-15.50-16.21-16.93-17.65-18.36-19.08-19.80-20.52-21.23-21.95-22.67-23.38-24.10-24.82-25.53
76
19-6.00-6.79-7.58-8.38-9.17-9.96-10.75-11.54-12.34-13.13-13.92-14.71-15.50-16.30-17.09-17.88-18.67-19.46-20.25-21.05-21.84-22.63-23.42-24.21-25.01-25.80-26.59-27.38-28.17-28.97-29.76
77
20-8.15-9.02-9.89-10.76-11.63-12.50-13.37-14.25-15.12-15.99-16.86-17.73-18.60-19.47-20.34-21.21-22.08-22.95-23.82-24.69-25.56-26.43-27.30-28.18-29.05-29.92-30.79-31.66-32.53-33.40-34.27
78