Candela to Lumen Converter

Candela (cd) measures light intensity in a specific direction (lumens per steradian), while lumens (lm) measure total light output in all directions. A 1000 lumen bulb might be 80 cd with a wide 120° beam or 2000+ cd with a narrow 15° spot beam. Candela tells you how bright light appears when looking at it; lumens tell you total light produced.

Use the formula: Lumens = Candela × Solid Angle (steradians). For beam patterns, solid angle = 2π(1 - cos(θ/2)) where θ is beam angle. For a 30° spot: Ω ≈ 0.21 sr, so 1000 cd × 0.21 = 214 lumens. For a full sphere (isotropic): Ω = 4π ≈ 12.57 sr, so 1000 cd = 12,566 lumens.

A steradian (sr) is a unit of solid angle - the 3D equivalent of radians. A full sphere contains 4π (≈12.57) steradians. A hemisphere is 2π sr. A typical spotlight with 30° beam angle covers about 0.21 sr. Solid angle determines how spread out light is, connecting candela (intensity) to lumens (total output).

Narrow beams (10-25°) concentrate light for accent lighting, spotlights, and task areas - high candela from fewer lumens. Wide beams (60-120°) spread light for general illumination - lower candela from same lumens. Match beam to use: narrow for artwork/products, medium (25-40°) for general spotlights, wide for ambient fill lighting.

LED indicators: 0.001-0.1 cd. Candle flame: 1 cd. 60W incandescent: 65-80 cd average. Car headlight (low beam): 2,500-10,000 cd. LED spot (35W): 5,000-15,000 cd. Stadium floodlight: 100,000+ cd. Lighthouse: 1,000,000+ cd. Higher candela means more intensity in the viewing direction.

Beam angle concentrates or spreads the same total light. A 1000 lumen LED at 15° beam produces ~5,500 cd peak intensity. The same 1000 lumens at 120° beam produces only ~100 cd. Narrow beams appear brighter at center but illuminate smaller areas. Choose based on whether you need intensity (narrow) or coverage (wide).