About the Lumens to Millicandela Calculator
Small indicator LEDs are often rated in millicandela (mcd), while bigger lamps and torches are rated in lumens. To compare them you need the viewing angle, because the same light squeezed into a narrow beam looks far more intense head-on. This calculator spreads the lumens evenly over a cone with the angle you enter, works out the solid angle in steradians, and gives the intensity in millicandela and candela. It is designed for LED datasheets, hobby electronics and lighting projects.
Updated October 2026
How to use the Lumens to Millicandela Calculator
- 1Enter the luminous flux in lumens.
- 2Enter the full viewing angle in degrees from the datasheet.
- 3Read the intensity in millicandela.
- 4Check the candela and steradian rows.
- 5Copy the result for your notes or parts list.
Why LED makers quote mcd
Through-hole and SMD indicator LEDs are mostly looked at directly, so the brightness straight ahead matters more than the total light. That is exactly what candela measures. A 5 mm LED with a narrow 15° lens can show 20,000 mcd yet put out less than a lumen, while a wide-angle LED of the same chip may show only 2,000 mcd.
The maths behind it
The light is assumed to fill a cone. The solid angle of a cone with full angle θ is Ω = 2π(1 − cos(θ/2)) steradians. Intensity is flux divided by solid angle, so candela = lumens ÷ Ω and millicandela = 1,000 × that.
- 10° cone: 0.0239 sr
- 30° cone: 0.2141 sr
- 60° cone: 0.8418 sr
- 120° cone: π sr ≈ 3.1416
- 360°: 4π sr ≈ 12.566
Choosing LEDs with this calculator
When a project needs a certain brightness from a certain distance, decide the lux you want, convert it to candela at that distance, then use this tool in reverse to see which lumen rating and angle can deliver it. For signs and indicators seen from the side, prefer wide angles even though the mcd figure looks smaller.
Datasheet tips
Datasheets usually give mcd at a stated test current, often 20 mA. Driving the LED at a lower current lowers the light roughly in proportion, so scale the lumens before converting. Also check whether the lumens figure is typical or minimum; using the minimum gives a safer estimate for designs that must be readable in daylight.
Phone or computer
Type on any device; the answer updates instantly and nothing leaves the page. Brightness changes with the beam angle, so keep that value close. Convert back with the Millicandela to Lumens Calculator, use the Lumens to Candela Calculator for larger values, and choose a resistor for a small LED with the LED Resistor Calculator.
Features
- Lumens to mcd and candela
- Uses the LED's full viewing angle
- Shows the solid angle in steradians
- Handles angles up to 360°
- Copy result
- Free and runs offline once loaded
Frequently asked questions
How do I convert lumens to millicandela?
mcd = 1,000 × lumens ÷ (2π × (1 − cos(angle ÷ 2))). A 2 lm LED with a 30° viewing angle gives about 9,342 mcd.
Why do I need the viewing angle?
Millicandela measures intensity in one direction. The narrower the beam, the more the same lumens are concentrated, so the mcd figure rises sharply as the angle shrinks.
What is the viewing angle on a datasheet?
Usually written 2θ½, it is the full angle at which the brightness falls to half of the on-axis value. Use that full angle here, not the half angle.
Is the result exact?
It assumes the light is spread evenly across the cone. Real LEDs are brightest on the axis and fade towards the edge, so the peak mcd on the datasheet is often higher than this average.
How many mcd is 1 lumen?
With a 120° beam, 1 lm is about 318 mcd; with a 30° beam it is about 4,671 mcd; with a 10° beam about 41,800 mcd.
Can I convert mcd back to lumens?
Yes, our Millicandela to Lumens calculator does the reverse with the same formula.