By Zencalcy Editorial TeamLast reviewed About us
The normal force is the perpendicular push a surface gives an object resting on it. On level ground it balances the object's weight; on a slope only the component of weight perpendicular to the surface has to be balanced, so the normal force is smaller.
Find the support force on a flat surface or an incline.
Flat: N = m g Incline: N = m g cos θ
This assumes no other vertical forces and a frictionless or static object. An extra downward push, another load, or an accelerating surface would change the normal force.
| Symbol | Meaning |
|---|---|
| N | Normal force perpendicular to the surface, in newtons. |
| m | Mass of the object, in kilograms. |
| g | Standard gravity, 9.80665 m/s². |
| θ | Angle of the incline above the horizontal. |
A 10 kg block on a 30° ramp has a weight of 98.07 N. The normal force is 98.07 × cos 30° = 84.93 N; the remaining 49.04 N acts down the slope.
Continue with the Rocket Equation Calculator, Tension Calculator, or the Rocket Thrust Calculator — or browse more dynamics tools and all physics calculators.
Only on a level surface with no other vertical forces. On an incline it is mg cos θ, and in an accelerating lift it is m(g + a).
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026