Luminance Converter

1. Enter the value you want to convert.
2. Choose the from unit.
3. Choose the to unit.
4. Read the result and the conversion rate.

Here is what each result means:

Luminance is how bright a surface looks to the eye, measured as light leaving an area in a given direction. The SI unit is the candela per square metre, widely called the nit, especially for screens. A phone in a dark room might run at 2 nits, an office monitor at 300 nits, and a bright high dynamic range television can peak above 1,000 nits.

Several older units describe the same quantity. The stilb is one candela per square centimetre, so a large 10,000 nits. The lambert and foot-lambert come from a different definition that folds in a factor of pi, because they describe a perfectly diffuse surface. The apostilb and millilambert are smaller relatives. These units survive in display, cinema and lighting standards, which is why a single brightness figure might be quoted several ways.

This converter bridges every unit through the candela per square metre. It multiplies your value by the number of candela per square metre in its unit, then divides by the number in the target unit. Because each unit has a fixed value, the conversions are exact and never change.

Luminance should not be confused with illuminance. Illuminance, in lux, is light arriving on a surface. Luminance, in candela per square metre, is light leaving a surface toward the eye, which is what makes a screen or a wall look bright. This converter deals only with luminance units.

It converts through the candela per square metre, the SI unit of luminance.

1. Your value is multiplied by its unit's value in candela per square metre.
2. That gives the luminance in candela per square metre, the common base.
3. Dividing by the target unit's value gives the result.

For the light-on-a-surface side, see the illuminance converter and the power converter.

Convert 300 nit to foot-lamberts.

Result: 300 candela per square metre is about 87.6 fL, since one foot-lambert is about 3.426 nits. That is a typical desktop monitor brightness, whichever unit a display standard happens to use.

Every unit has a fixed value in candela per square metre.

The lambert and its relatives carry a factor of pi from their diffuse-surface definition, which is why they are not round numbers against the nit. The stilb is large at 10,000 nits, suited to intense sources, while the apostilb is small, for dim surfaces.

Luminance spans a wide range, from a dim phone to bright signage.

Comparing surfaces this way shows why the units persist. Cinema standards are often quoted in foot-lamberts, while screen makers use nits, and the converter lets you move between whichever a standard or datasheet uses.

The Two Units

The ratio between the from-unit and to-unit sets the result; each has a fixed value in cd/m2.

The Factor of Pi

Lambert-family units include pi from their diffuse-surface definition, so they are not round against the nit.

The Size of the Unit

A large unit like the stilb gives small numbers, while a small one like the apostilb gives large ones.

Displays

Compare a screen brightness quoted in nits with a standard given in foot-lamberts.

Cinema and Projection

Convert projector luminance between foot-lamberts and candela per square metre.

Older References

Turn a stilb or lambert figure from an older text into modern nits.

1. Confusing Luminance and Illuminance

Luminance is light leaving a surface; illuminance in lux is light arriving on one.

2. Forgetting the Pi Factor

Lambert and foot-lambert include pi, so they do not convert to round nit values.

3. Mixing Nit and Stilb

A stilb is 10,000 nits. Treating them as equal is a large error.

4. Wrong Direction

Check which unit is the from and which is the to; swapping them inverts the result.

5. Confusing Nits with Lumens

Lumens measure total output; nits measure brightness per square metre of a surface.

Conversions use fixed factors relative to the candela per square metre.

A nit is one candela per square metre, the SI unit of luminance. Screen makers use it for brightness; an office monitor is around 300 nits.

About 3.426 nits. So a cinema white level of 14 foot-lamberts is about 48 nits. To convert foot-lamberts to nits, multiply by 3.426.

Luminance is light leaving a surface toward the eye, in candela per square metre. Illuminance is light arriving on a surface, in lux.

A stilb is one candela per square centimetre, equal to 10,000 nits. It is a large unit from the older centimetre-gram-second system.

They are defined for a perfectly diffuse surface, and the geometry of light spreading over a hemisphere brings in a factor of pi.

From about 2 nits in the dark up to 600 nits or more in sunlight. High dynamic range phones can peak even higher for small highlights.

Luminance is the measured quantity; brightness is how we perceive it. They track together, but perception also depends on the surroundings.

Cinema and projection. Screen luminance standards, such as 14 foot-lamberts for film white, are often quoted in this unit.

No. The calculation runs in your browser and nothing you enter is stored or sent anywhere, unless you choose Save, which keeps the result only on this device.

• Luminance (Wikipedia).
• Candela per square metre (Wikipedia).
• Foot-lambert (Wikipedia).