The Toolbox — Charts

Drone & Rocketry

Rocket motor classification, HPR certification levels, and drone frame/prop size reference.

Rocket Motor Classification

Each class doubles the total impulse of the previous. HPR certification through NAR or Tripoli required for H motors and above.

Class	Total Impulse	Avg Thrust	HPR Level	Notes
A	1.26–2.5 N·s	~2N	None	Beginner — small model rockets
B	2.51–5.0 N·s	~4N	None	Small rockets, higher altitude
C	5.01–10 N·s	~8N	None	Mid-power entry, Estes C6
D	10.01–20 N·s	~15N	None	Larger model rockets
E	20.01–40 N·s	~28N	None	High-performance LPR / MPR entry
F	40.01–80 N·s	~55N	None	Mid-power rocketry
G	80.01–160 N·s	~110N	None	HPR threshold (H starts HPR)
H	160.01–320 N·s	~220N	Level 1	HPR Level 1 certification required
I	320.01–640 N·s	~440N	Level 1	HPR Level 1
J	640.01–1280 N·s	~880N	Level 2	HPR Level 2 certification required
K	1280.01–2560 N·s	~1760N	Level 2	HPR Level 2
L	2560.01–5120 N·s	~3500N	Level 2	HPR Level 2
M	5120.01–10240 N·s	~7000N	Level 3	HPR Level 3 certification required
N	10240.01–20480 N·s	~14000N	Level 3	HPR Level 3
O	20480.01–40960 N·s	~28000N	Level 3	HPR Level 3 — commercial launch sites

Frame size is measured motor-to-motor diagonally. Prop size should match frame size for optimal efficiency.

Frame Size	Prop Size	Cell Count	Notes
65mm Whoop	31mm	1S	Indoor micro
75mm Whoop	40mm	1S–2S	Indoor/outdoor micro
2"	2 inch	2S–3S	Micro freestyle
3"	3 inch	3S–4S	Micro/mini freestyle
3.5"	3.5 inch	3S–4S	Sub-250g builds
4"	4 inch	3S–4S	Mid-size freestyle
5"	5 inch	4S–6S	Standard FPV — most popular
6"	6 inch	4S–6S	Long range, efficiency
7"	7 inch	4S–6S	Long range cruiser
10"	10 inch	4S–6S	Heavy lift, cinematic