About the Lumens to Candela Calculator
This calculator converts lm to cd. lm is lumens, the total amount of visible light a lamp gives out, and cd is candela, the brightness of a light in one particular direction. It computes the solid angle of the beam and divides the lumens by it. Enter your figures and the answer appears at once, together with a few related values, and you can copy the result with one tap. The sums are done in your browser and nothing is sent anywhere.
Updated October 2026
How to use the Lumens to Candela Calculator
- 1Enter the value in lm.
- 2Fill in the other boxes that the lm to cd calculation needs, such as time, voltage or power factor.
- 3Read the answer in the large result box.
- 4Check the extra rows for related values.
- 5Press Copy result to keep it.
When you need lm to cd
Lumens tell you the total light a lamp gives out in all directions. Candela tells you how bright it is in one direction. A narrow beam squeezes the same lumens into a smaller angle, so it has a higher candela value. To compare a spotlight with a bulb, you need the beam angle.
The beam angle is printed on the packaging of spot and downlight lamps, for example 36°, 60° or 120°. A bulb that lights all directions equally has an angle of 360°, and its intensity is the lumens divided by 4π, or about 63.7 cd for 800 lm.
How the lm to cd sum works
Candela = lumens ÷ solid angle, where the solid angle is 2π × (1 − cos(angle ÷ 2)) steradians. An 800 lm spot with a 120° beam has a solid angle of π steradians, so its intensity is about 254.6 cd.
The displayed answer is rounded to six significant figures, but the sum itself is not rounded, so converting lm to cd and back again gives you the number you started with.
- Beam angle is on the packaging
- 360° gives lumens ÷ 4π
- Narrow beams have higher candela
Mistakes to avoid when converting lm to cd
The calculation assumes the light is spread evenly across the cone. Real lamps are brighter at the centre and dimmer at the edge, so the result is an average over the beam. Use the manufacturer's candela figure when you have it.
On phone and computer
On a phone, type in the boxes one after another and read the cd result underneath; the Copy button puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the cd value move. The lm to cd page works the same on both. Go back with Candela to Lumens Calculator, or work from illuminance with Lux to Candela Calculator. Lumens to Lux Calculator and Lumens to Watts Calculator fill in the other lighting questions.
Features
- lm to cd in one step
- Related values shown with the answer
- Clear messages for impossible inputs
- Copy the result with one tap
- Private: nothing is uploaded
- Works on phone and computer
Frequently asked questions
How do I convert lm to cd?
Candela = lumens ÷ solid angle, where the solid angle is 2π × (1 − cos(angle ÷ 2)) steradians. An 800 lm spot with a 120° beam has a solid angle of π steradians, so its intensity is about 254.6 cd.
What is the formula for lm to cd?
Candela = lumens ÷ solid angle, where the solid angle is 2π × (1 − cos(angle ÷ 2)) steradians. The calculator applies it exactly and rounds only the displayed answer.
What is the difference between lm and cd?
lm is lumens, the total amount of visible light a lamp gives out. cd is candela, the brightness of a light in one particular direction. They measure different things, which is why converting from lm to cd needs more than a simple multiplication in some cases.
What is the solid angle?
A measure of a cone of light in steradians. A full sphere is 4π, about 12.57 sr. The calculator shows the value for your beam angle.
Why does a narrower beam give more candela?
Because the same lumens are packed into a smaller cone, so each direction inside it gets more light.
Is this lm to cd calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so the figures you type are not uploaded or stored. It is meant for planning and learning; for wiring or safety work, check the result against your equipment's rating plate and local rules.