Laminar Flame Thickness Calculator

Laminar Flame Thickness Calculator

Flames are thin - typically well under a millimeter for premixed hydrocarbon combustion - and that thickness is set by a balance between how fast heat diffuses forward and how fast the flame itself is propagating.

The Formula

δ = α / S_L

Where α is thermal diffusivity and S_L is laminar burning velocity.

Reference Table

Illustrative flame thickness by burning velocity, at 20 mm²/s thermal diffusivity

Burning Velocity	Flame Thickness
0.2 m/s	0.10 mm
0.4 m/s	0.05 mm
0.8 m/s	0.025 mm

Faster flames are thinner flames - doubling burning velocity halves the estimated thickness, since a faster-propagating flame gives heat less time to diffuse ahead of the reaction zone. Related: Flame Quenching Distance Calculator, which uses this thickness value directly.