Register Spread Calculator
Lateral spread angle of a supply register.
Enter your values
ⓘ Live results
Results
- Estimated spread width
- 4.5 ft
- Pattern used
- med
- Coverage area at throw
- 45 sq ft
Quick answer
Spread is the register's lateral coverage width at its throw distance, generally 30-60% of the throw for adjustable-pattern registers.
Spread width ≈ throw x spread factor
How to use the Register Spread Calculator
- 1Enter the register's rated or calculated throw distance.
- 2Select the deflection pattern — 1-way, multi-way or 4-way.
- 3Use the spread width to check the register covers the room width without concentrating air in one spot.
Worked example
Using the values the calculator loads with:
Inputs
- Throw distance10 ft
- Register patternMedium (2 or 3-way)
Results
- Estimated spread width4.5 ft
- Pattern usedmed
- Coverage area at throw45 sq ft
Frequently asked questions
Why do 4-way registers spread more?
They deflect air outward in multiple directions instead of one narrow jet, trading throw distance for wider, gentler coverage.
What if a room is very wide?
Use a wider-pattern register or add a second register rather than relying on a single narrow-pattern throw.
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.