Quick answer
Luminance units convert through candela per square metre (nits). 1 foot-lambert equals 3.4263 cd/m².
Enter a value and choose the units. The calculator returns the converted luminance.
Related tools: Volume Converter: Convert litres, gallons, cups, spoons and more. Weight Converter: Convert kilograms, pounds, ounces, stone and more. Length Converter: Convert between metric and imperial lengths.
How to use the Luminance Converter
- Enter value.
- Choose from: Candela per m² (nit), Kilocandela per m², Candela per ft², Foot-lambert (fL), Lambert and Stilb (cd/cm²).
- Choose to: Candela per m² (nit), Kilocandela per m², Candela per ft², Foot-lambert (fL), Lambert and Stilb (cd/cm²).
- Enter decimal places (between 0 and 10). It starts at 4.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Value | A number | — |
| From | Choose one: Candela per m² (nit); Kilocandela per m²; Candela per ft²; Foot-lambert (fL); Lambert; Stilb (cd/cm²) | Starts at Candela per m² (nit) |
| To | Choose one: Candela per m² (nit); Kilocandela per m²; Candela per ft²; Foot-lambert (fL); Lambert; Stilb (cd/cm²) | Starts at Kilocandela per m² |
| Decimal places | A number | ≥ 0, ≤ 10, starts at 4 |
Formula and method
Formula
result = value × (factor of source ÷ factor of target), base unit: candela per square metre
IEEE-754 double precision; displayed to the chosen number of decimal places (default 4). Very small or large results are shown in scientific notation.
Every unit is defined by an exact or published factor to the base unit (candela per square metre). The value is multiplied by the source factor and divided by the target factor.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Value = 1; From = Foot-lambert (fL); To = Candela per m² (nit); Decimal places = 4.
| Result | Value |
|---|---|
| Foot-lambert (fL) → Candela per m² (nit) | 3.4263 |
| Input | 1 Foot-lambert (fL) |
Example 2
Inputs: Value = 1; From = Candela per ft²; To = Candela per m² (nit); Decimal places = 4.
| Result | Value |
|---|---|
| Candela per ft² → Candela per m² (nit) | 10.7639 |
| Input | 1 Candela per ft² |
Example 3
Inputs: Value = 1; From = Stilb (cd/cm²); To = Kilocandela per m²; Decimal places = 4.
| Result | Value |
|---|---|
| Stilb (cd/cm²) → Kilocandela per m² | 10 |
| Input | 1 Stilb (cd/cm²) |
The first line is the headline result (foot-lambert (fL) → Candela per m² (nit)). Below it the luminance Converter lists input, which describe the same case from other angles. IEEE-754 double precision; displayed to the chosen number of decimal places (default 4). Very small or large results are shown in scientific notation.
Unit reference
Each unit expressed in the base unit used for the calculation. Conversions go through this base unit, so any unit can be converted to any other in the table.
| Unit | Equals (in candela per square metre) |
|---|---|
| Candela per m² (nit) | 1 |
| Kilocandela per m² | 1000 |
| Candela per ft² | 10.76391042 |
| Foot-lambert (fL) | 3.4262591 |
| Lambert | 3183.098862 |
| Stilb (cd/cm²) | 10000 |
Typical values
A phone screen is 400 to 1,000 nits, a cinema screen about 48 nits (14 fL) and HDR monitors reach 1,000 nits or more. 14 fL is 48 cd/m².
Not illuminance
Luminance is how bright a surface appears; illuminance is the light falling on it. Displays are specified in luminance, rooms in illuminance.
How the result changes with value
Holding every other input at the first worked example, this table changes only value. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Value | Foot-lambert (fL) → Candela per m² (nit) | Input |
|---|---|---|
| 0.5 | 1.7131 | 0.5 Foot-lambert (fL) |
| 1 | 3.4263 | 1 Foot-lambert (fL) |
| 2 | 6.8525 | 2 Foot-lambert (fL) |
| 4 | 13.705 | 4 Foot-lambert (fL) |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Value: left empty shows "Enter value." beside that field and no result.
Choosing between the Luminance Converter and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Volume Converter](/converters/volume-converter/) | value, from and to | US gallon → Litre (L) |
| [Weight Converter](/converters/weight-converter/) | value, from and to | Pound (lb) → Gram (g) |
| [Length Converter](/converters/length-converter/) | value, from and to | Mile (mi) → Kilometre (km) |
| [Energy Converter](/converters/energy-converter/) | value, from and to | Megawatt-hour (MWh) → Kilowatt-hour (kWh) |
| [Power Converter](/converters/power-converter/) | value, from and to | Horsepower (mechanical) → Watt (W) |
Background: unit conversion
Many customary units are defined exactly in terms of metric ones: since the 1959 International Yard and Pound Agreement an inch is exactly 2.54 cm and a pound is exactly 0.45359237 kg (NIST SP 811 lists these). So most length and mass conversions are exact apart from the rounding of the displayed result.
To convert, multiply the value by the source unit's factor to reach the base unit, then divide by the target unit's factor; the unit table on this page lists every factor used. Temperature and fuel economy are the exceptions, because they are not simple multiples.
Assumptions and limitations
- Negative values are allowed
- Zero converts to zero (except L/100 km, where zero is invalid)
- Units from different quantities cannot be converted
- Very large or tiny results switch to exponent notation
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for value to confirm this.
Frequently asked questions
What is a nit?
One candela per square metre.
How many nits in a foot-lambert?
1 foot-lambert is 3.4263 cd/m² (nits), so a 14 fL cinema screen is about 48 nits.
What is the SMPTE cinema standard?
About 14 foot-lamberts (48 nits).
What does the Luminance Converter calculate?
Convert cd/m², foot-lamberts, lamberts and more. It returns Foot-lambert (fL) → Candela per m² (nit) and Input.
What formula does the Luminance Converter use?
result = value × (factor of source ÷ factor of target), base unit: candela per square metre. Every unit is defined by an exact or published factor to the base unit (candela per square metre).
What does the “From” option change?
It sets how the luminance is worked out. The choices are Candela per m² (nit), Kilocandela per m², Candela per ft², Foot-lambert (fL), Lambert and Stilb (cd/cm²).
What is an example of a luminance result?
With value 1, from Foot-lambert (fL), to Candela per m² (nit) and decimal places 4, the foot-lambert (fL) → Candela per m² (nit) is 3.4263.
Where does the method come from?
The method follows: NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B (foot-lambert, lambert, stilb and cd/m2 conversion factors).
Related calculators
- Volume Converter — Convert litres, gallons, cups, spoons and more.
- Weight Converter — Convert kilograms, pounds, ounces, stone and more.
- Length Converter — Convert between metric and imperial lengths.
- Energy Converter — Convert joules, calories, kWh, BTU and more.
- Power Converter — Convert watts, kilowatts, horsepower and BTU per hour.
- Temperature Converter — Celsius, Fahrenheit, Kelvin and Rankine.
Sources
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Appendix B (foot-lambert, lambert, stilb and cd/m2 conversion factors)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.