# FK vs IK: when should I use each?

> Use IK when part of the body must stay in contact with something: feet on the ground, hands on a table, a hand holding a rail. Use FK for free motion: arms swinging, tails, heads turning, and overlapping action. Many animators block poses with IK and polish arcs with FK, and use IK/FK switching when a limb changes from free to planted.

Updated November 2026. Source: https://www.exodeui.com/questions/fk-vs-ik-when-to-use-each/

## Key takeaways

- IK for contact: planted feet, hands on objects, pushing and pulling
- FK for free motion: swings, waves, follow-through
- Walk cycles: IK legs, FK arms is a common setup
- IK can produce straight, mechanical paths; check arcs
- Switch per limb when contact begins or ends

## Frequently asked questions

### Should I animate a walk cycle in IK or FK?

A common setup is IK for the legs so feet stay planted, and FK for the arms so they swing in arcs.

### Why does my IK knee flip?

The solver chose the other bend direction as the leg straightened. Set the bend direction or add a pole target if your tool supports it.

### Is IK slower to animate?

Usually faster for contact poses, but it may need extra keys to keep natural arcs.

### Can I mix IK and FK on one character?

Yes. Most rigs mix them per limb, and many tools allow switching or blending.

## Related

- [What is FK and IK in animation?](https://www.exodeui.com/questions/what-is-fk-and-ik-in-animation)
- [What is IK/FK switching?](https://www.exodeui.com/questions/what-is-ik-fk-switching)
- [Best 2D rigging software with IK and FK](https://www.exodeui.com/best-2d-rigging-software-ik-fk)
- [Spine vs Rive vs Moho](https://www.exodeui.com/questions/spine-vs-rive-vs-moho)