Light Intensity Converter — Candela & Candlepower Converter
Convert luminous intensity between different units including candela, candlepower, hefnerkerze, carcel, lumen/steradian, and more. Essential for lighting design, photometry, and optical engineering. See also our Image Resolution Converter and Frequency to Wavelength Converter.
Value:
How to Convert Light Intensity
- Enter the luminous intensity value in the input field above.
- Select the unit you are converting from in the "From" dropdown menu.
- Select the unit you want to convert to in the "To" dropdown menu.
- The result will automatically appear in the result field.
- Use the copy button to copy the result to your clipboard.
- Click any conversion in the list below to quickly select those units.
Light Intensity Formula
Luminous Intensity Definition:
Iv = dΦv/dΩ
Where:
Iv = Luminous intensity (cd)
Φv = Luminous flux (lm)
Ω = Solid angle (sr)
Unit Relationships:
1 cd = 1 lm/sr (lumen per steradian)
1 cd ≈ 1.019 cp (candlepower)
1 cp ≈ 0.981 cd
1 cd ≈ 1.107 HK (hefnerkerze)
1 HK ≈ 0.903 cd
1 carcel ≈ 9.74 cd
1 bougie decimale = 1 cd
Metric Prefixes:
1 kcd = 1000 cd
1 mcd = 0.001 cd
1 μcd = 10⁻⁶ cd
1 Mcd = 10⁶ cdExample Conversion
Problem: Convert 100 candlepower to candela and hefnerkerze.
Given: Iv = 100 cp
Solution:
• To candela: 100 cp × 0.981 cd/cp = 98.1 cd
• To hefnerkerze: 98.1 cd ÷ 0.903 cd/HK = 108.64 HK
Answer: 100 cp = 98.1 cd = 108.64 HK
Technical Details
Luminous intensity measures the power emitted by a light source in a particular direction, weighted by the luminosity function representing human eye sensitivity. The candela (cd) is one of the seven SI base units, defined since 2019 by fixing the luminous efficacy of 540 THz radiation at 683 lm/W. One candela is approximately the luminous intensity of a common candle.
Historical units like candlepower (based on spermaceti candles), hefnerkerze (based on the Hefner lamp burning amyl acetate), and carcel (based on the Carcel oil lamp) were standards before the international candela was adopted. The bougie decimale was the French standard equivalent to the modern candela. These historical units remain relevant when interpreting older photometric literature.
Light Intensity Reference Table
| Light Source | Typical Intensity | Application |
|---|---|---|
| Single LED indicator | 5-50 mcd | Electronics displays |
| Candle flame | 1 cd | Historical reference |
| Household LED bulb | 70-100 cd | General lighting |
| Car headlight (low beam) | 10-30 kcd | Automotive |
| Car headlight (high beam) | 40-100 kcd | Automotive |
| Searchlight | 0.5-2 Mcd | Military/marine |
| Lighthouse | 1-5 Mcd | Navigation |
| Stadium floodlight | 100-500 kcd | Sports lighting |
Frequently Asked Questions
What is the difference between candela and candlepower?
Candlepower (cp) is an older unit approximately equal to 0.981 candela. The candela replaced candlepower as the standard unit. In modern usage, "candlepower" is often used informally as a synonym for candela, though technically 1 cp = 0.981 cd.
How is the candela defined?
Since 2019, the candela is defined by fixing the luminous efficacy of monochromatic radiation at frequency 540 × 10¹² Hz (green light) at exactly 683 lumens per watt. This makes it independent of any physical artifact.
What is a hefnerkerze?
The hefnerkerze (HK) was a German unit of luminous intensity based on the Hefner lamp, which burned amyl acetate with a specific flame height. One HK equals approximately 0.903 candela. It was the German standard from 1884 until replaced by the international candela.
What is the difference between luminous intensity and luminous flux?
Luminous intensity (candela) measures light output per unit solid angle in a specific direction. Luminous flux (lumen) measures total light output in all directions. A 1-candela isotropic source emits 4π ≈ 12.57 lumens total.
Why is lumen/steradian equal to candela?
By definition, luminous intensity equals luminous flux per unit solid angle: Iv = Φv/Ω. Since the unit of flux is lumen (lm) and solid angle is steradian (sr), the candela is dimensionally equivalent to lm/sr. They are the same unit expressed differently.
Objective of Measurement:
Measurement is the most important aspect of our life. We use measurement in science, engineering, business trading, personal life, education, and more other fields. As technology is growing day by day so we need a highly accurate and easy convenient global measuring system in each and every field. It is essential to use standard measurement in every field that everyone to be sure that they not get cheated.
History of Measurement:
In history for measurement people used the human body as a tool. For measuring length used forearm, hand, foot & finger as a unit. The foot, finger is a subdivided shorter unit of a length. This type of measurement is not accurate cause different in size of the arm & finger for different people & some of the countries still using it. In history, there were lots of measuring systems developed but mostly used imperial, the metric system of measurement. We use these systems for measure distances, volume, weight, speed, area etc. Due to this a major problem everyone is facing while doing trading between the countries. A huge improvement in civilization, It necessary to improve measuring standards. Nowadays International Standard (SI) units are used as a global measurement system.
Light Intensity Conversion - Unit Converter:
Our light intensity conversion converter convert candela [cd], millicandela [mcd], kilocandela [kcd], candlepower [cp], hefnerkerze [HK], carcel [carcel], bougie decimale [bd], lumen/steradian [lm/sr], microcandela [μcd], megacandela [Mcd] vice versa with metric conversion.
Light intensity conversions & its abbreviations
| Unit | Abbreviation | Unit | Abbreviation |
|---|---|---|---|
| candela | cd | millicandela | mcd |
| kilocandela | kcd | candlepower | cp |
| hefnerkerze | HK | carcel | carcel |
| bougie decimale | bd | lumen/steradian | lm/sr |
| microcandela | μcd | megacandela | Mcd |
Complete list of Light intensity conversion units and its conversion.
1 candela [cd] = 1.0194 candlepower [cp]
1 candlepower [cp] = 0.981 candela [cd]
1 candela [cd] = 1000 millicandela [mcd]
1 candela [cd] = 1.107 hefnerkerze [HK]
1 hefnerkerze [HK] = 0.903 candela [cd]
1 carcel = 9.74 candela [cd]
1 candela [cd] = 1 lumen/steradian [lm/sr]
1 kilocandela [kcd] = 1000 candela [cd]