Millicandela to Lumens

About the Millicandela to Lumens

A millicandela to lumens calculator converts luminous intensity in millicandela (mcd) — the standard unit for component LED intensity ratings — to total luminous flux in lumens by multiplying by the solid angle of the LED beam. Component LEDs, LED indicators, and small-package LEDs are universally specified in millicandela at a standard viewing angle (typically ±15° or ±30°) rather than lumens, because the beam is narrow and directional. Understanding the mcd-to-lumens conversion is essential for LED engineers and product designers who need to know the actual light output of LED indicators for display panels, automotive lighting, signal lights, and industrial control equipment. The millicandela figure on a datasheet tells you how intensely the LED shines directly forward; the lumens figure tells you how much total light it produces across its entire beam angle. Our calculator uses the viewing angle from the LED datasheet to compute the solid angle (steradians) and derive the total lumens. For typical component LEDs: 1,000 mcd at ±20° half-angle ≈ 0.4 lm. 20,000 mcd at ±20° ≈ 8 lm.

How It Works

Step 1: Convert mcd to cd: cd = mcd / 1,000. Step 2: Calculate solid angle from beam half-angle θ: Ω = 2π(1 - cos θ). Step 3: lm = cd × Ω. Example: LED datasheet shows 5,000 mcd at ±25° half-angle. Step 1: cd = 5,000 / 1,000 = 5 cd. Step 2: Ω = 2π(1 - cos25°) = 2π(1 - 0.9063) = 2π × 0.0937 = 0.5889 sr. Step 3: lm = 5 × 0.5889 = 2.94 lm. For reference: a standard household LED nightlight uses 10-30 lm; a reading LED desk lamp uses 300-600 lm. So 2.94 lm is appropriate for an indicator or status light but far below room lighting levels. Common component LED outputs: standard 5mm red LED (typical 3,000 mcd, ±15°): ≈ 0.49 lm. High-brightness white 5mm LED (20,000 mcd, ±20°): ≈ 4.5 lm. High-power LED module (1W, 100 lm/W): ≈ 100 lm.

Tips & Best Practices

• ✓Viewing angle conventions on LED datasheets: the 2θ½ specification is the full angle at which intensity drops to 50% of peak (the half-power angle). The half-angle for the solid angle formula is 2θ½ / 2 = θ½. A datasheet listing "viewing angle 30°" means ±15° from center — use 15° as the half-angle in the formula.
• ✓Lambertian emission: many LEDs approximate Lambertian emission where cd varies as cos(θ) from peak. For such LEDs, the half-power angle is always 60° (±60° viewing angle), and lm = cd_peak × π. This applies to many bare LED dies and Lambertian-lens LEDs.
• ✓Surface-mount device (SMD) LEDs: 0402, 0603, 0805 SMD indicator LEDs are typically rated 50-500 mcd at ±60° half-angle. At 500 mcd, ±60°: Ω = 2π(1-cos60°) = 2π × 0.5 = π sr ≈ 3.14 sr. lm = 0.5 × 3.14 = 1.57 lm. These are not lighting LEDs — they are visible only as indicator lights.

Who Uses This Calculator

LED engineers converting component datasheet mcd values to lumens for system-level optical design. PCB designers verifying that indicator LED brightness meets visibility requirements for panel illuminance targets. Product designers comparing LED indicator brightness options across different manufacturers. Lighting engineers working with legacy LED specifications that use mcd rather than modern lm ratings.