About the Fireworks Safety Distance Calculator
This tool estimates the minimum spectator separation distance for an aerial fireworks shell based on its nominal diameter. It is useful for event organizers, safety reviewers, and anyone learning how shell size relates to clearance distance under the NFPA 1123 70-feet-per-inch rule.
How to use this calculator
- Enter the firework shell diameter in inches.
- Use a positive nominal shell size, such as 2, 3, 4, 6, or 8.
- Read the calculated minimum spectator distance in feet.
- Check the converted distance in meters shown below the main result.
- Change the diameter to instantly recalculate the distances.
How it works
The calculator uses one input: the firework shell diameter in inches. It assumes the applicable clearance rule is 70 feet of minimum spectator distance for each inch of shell diameter.
The formula is: minimum distance in feet = shell diameter × 70. The calculator then converts that distance to meters using: meters = feet × 0.3048.
If the entered diameter is not a positive number, the calculator displays a prompt to enter a valid diameter instead of returning a distance. Results are educational estimates and are not a substitute for professional pyrotechnic planning, permitting, site inspection, weather assessment, or local authority guidance.
Example calculation
For a 3-inch aerial shell, multiply 3 by 70 to get 210 feet. Converting 210 feet to meters gives 210 × 0.3048 = 64.0 meters, so the estimated minimum spectator distance is 210 ft, or about 64.0 m.
Frequently asked questions
What does 70 feet per inch mean for fireworks?
It means the minimum spectator separation distance is estimated as 70 feet for every inch of aerial shell diameter.
What shell diameter should I enter?
Enter the nominal shell diameter in inches, such as 2, 3, 4, 6, or 8 inches, based on the shell being evaluated.
Does this calculator account for wind or site layout?
No. It only applies the diameter-based distance rule and does not account for wind, terrain, fallout area, launch angle, obstructions, or local permit requirements.
Is the meter conversion exact?
The calculator converts feet to meters using 1 foot = 0.3048 meters, then displays the result to one decimal place.
Can this result be used as final approval for a fireworks show?
No. Fireworks displays require qualified planning and compliance with applicable laws, codes, permits, and authority-having-jurisdiction requirements.