# How much horsepower do I need for my paramotor?

Assuming my full kit and I weigh 82kg total, I have estimated that I need 5hp. To calculate this, I used the formula:

weight force (W) is F = m g

W= 82kg*9.8 ms/2 =401.8 Newtons

Now, if the drag ratio is 9:1 that means that there is also 401.8 Newtons of Lift (L) and 45 Newtons of Drag (D): D= L / (L:D) 45= 401.8/9 So if 45 Newtons are required to be overcome drag, this is the thrust the engine must produce. Using a rule of thumb of 11 Newtons per Hp that equals 4.05 Hp. I rounded this up to 5hp for climbing.  Is my math correct? 5hp  seems low compared to paramotors on the market with 20+hp. I would also need approximately 10kg of thrust, 82/9=9.1 rounded up to 10

• An easy way to calculate the power is to think in the 'gravitational power' of the aircraft in a glide. If the horizontal speed is S, and the glide ratio (L/D) is R, the vertical sink speed V = S/R. Now, the power P involved is the weight W of the aircraft times that sink speed => P = W * V. For a given mass and L/D, the 'gravitational' power involved in the glide is the same s the power you'd need for straight and level, unaccelerated flight... Dec 4, 2022 at 17:52
• Make sure you have excess power to climb. You can figure ROC as a mirror image of glide ratio. So if you climb 1 to 9 @ 40 knots, climb vertical rate is around 4.5 knots or around 450 feet per minute. To provide safety margin, double hp required for level flight. Dec 4, 2022 at 18:16