So Squid peanut had so criticism on the last calc so I decided to try doing it from a different angle by comparing the Knight to the Mantis' size
https://www.thesprucepets.com/keeping-pet-mantids-1239208
According to the website Praying Mantes range from around 1 to 6 inches or 2.54 to 15.24 cm which will be our range, it also uses 2 to 3 inches or 5.08 to 7.62 cm which will act as mid-balls
In the image to the left the mantis is 174.27 px while the knight is 52.42 px
Knight's height low ball = 2.54*52.42/174.27 = 0.7640259367647904 cm
Knight's height low-mid ball = 5.08*52.42/174.27 = 1.528051874 cm
Knight's height high-mid ball = 7.62*52.42/174.27 = 2.29207781 cm
Knight's height high ball = 15.24*52.42/174.27 = 4.584155620588742 cm
Re-using Arbi's math but with different numbers again
Low ball:
0.7640259368/42 = 0.01819109373 cm per px
0.01819109373^3 * 142 * 400 * 114 = 38.97890385624740 cm^3
Going by violent frag as that's what's accepted.
69*38.97890385624740 = 2689.544366 J or 6.42816531090122E-07 Tons of TNT or 9-C+
Low-Mid ball:
1.528051874/42 = 0.03638218746 cm per px
0.03638218746^3*142*400*114 = 311.83123084997900 cm^3
69*311.83123084997900 = 21516.35492864860 J or 5.14253224872098E-06 Tons of TNT or 9-B
High-mid ball:
2.29207781/42 = 0.0545732812 cm per px
0.0545732812^3 * 142 * 400 * 114 = 1052.43040411868 cm^3
69*1052.43040411868 = 72617.69788418890 J or 1.73560463394333E-05 Tons of TNT or 9-B
High ball:
4.584155621/42 = 0.1091465624 cm per px
0.1091465624^3 *142 * 400 * 114 = 8419.44323294943000 cm^3
69*8419.44323294943000 = 580941.58307351100 J or 1.38848370715466E-04 Tons of TNT or 9-B+