Register Throw Calculator
Estimate register throw distance from velocity.
Enter your values
ⓘ Live results
Results
- Estimated throw
- 4.8 ft
- Core velocity used
- 500 FPM
- Terminal velocity
- 50 FPM
- Guidance
- Match throw to 3/4 of the distance to the opposite wall
Quick answer
Throw is the distance a supply jet travels before slowing to a chosen terminal velocity, commonly 50 or 150 FPM.
Throw ≈ k x sqrt(CFM x core velocity) simplified as core velocity ratio
How to use the Register Throw Calculator
- 1Enter the register CFM and its rated core (outlet) velocity from the catalog.
- 2Pick the terminal velocity that matches your comfort target.
- 3Compare the throw to the room dimensions to avoid drafts hitting occupants directly.
Worked example
Using the values the calculator loads with:
Inputs
- Register CFM120 CFM
- Core (outlet) velocity500 FPM
- Terminal velocity50 FPM (typical room)
Results
- Estimated throw4.8 ft
- Core velocity used500 FPM
- Terminal velocity50 FPM
- GuidanceMatch throw to 3/4 of the distance to the opposite wall
Frequently asked questions
What terminal velocity should I use?
50 FPM is standard for occupied zones; use 150 FPM only for checking maximum reach.
Why does throw matter?
Too little throw leaves stagnant zones; too much can blow directly on people or hit the far wall hard.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.