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Choose whether you want to work with intensity (cd), luminance (nits, lambert), or illuminance (lux, footcandle). Units only convert within the same quantity type.
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Lux ⇄ Nits Approximate Helper (Lambertian Surface)
Use this mini-helper when you want an approximate conversion between room lighting in lux and display brightness in nits. Remember: lux (illuminance) and nits (luminance) are a bit like apples 🍎 and oranges 🍊 – this only works under a simplified Lambertian assumption.
Approximate result: –
nits ≈ lux / π (π ≈ 3.1416)
Lux and nits measure different things: illuminance vs luminance. This helper assumes an ideal diffuse (Lambertian) surface and is not suitable for precise calibration, compliance work, or safety-critical design.
💡 Overview
If you’re comparing a lux reading from a light meter with a monitor spec in nits (cd/m²), the confusion isn’t the math—it’s that the units describe different physical quantities.
This page helps you convert within the right bucket—illuminance, luminance, or luminous intensity—and explains when you need extra context (distance, geometry, reflectance) before any “conversion” makes sense.
Quick navigation: for more converters, visit the Unit Converters hub.
🧮 Formula & Methodology
1) Don’t mix the three “light measurement families”
- Illuminance (lux, footcandle): how much light arrives on a surface (lm/m²).
- Luminance (nits = cd/m², lambert): how bright a surface appears (light leaving a surface per area).
- Luminous intensity (candela): how much light a source emits in a particular direction.
Information gain tip: If the unit has “per square meter” (cd/m²), you’re in luminance. If it’s “per square meter” but with lumens (lm/m²), you’re in illuminance. Candela alone is intensity.
2) Within the same family, conversions are pure scaling
Inside each family, the converter uses fixed factors (or SI-prefix scaling) with no geometry required:
result = value × (factor_from ÷ factor_to)
Quick reference table: conversions people look up most
| Conversion | Relationship | Notes (logic traps) |
|---|---|---|
| lux ↔ footcandle | 1 fc = 10.7639104167 lux 1 lux = 0.09290304 fc |
Both are illuminance, so this is a true unit conversion. |
| nits ↔ cd/m² | 1 nit = 1 cd/m² | “Nit” is just the common name for cd/m². |
| lambert ↔ nits (cd/m²) | 1 L ≈ 3183.0988618 cd/m² | Lambert is a luminance unit; don’t confuse with lux. |
Lux ⇄ nits: why the main converter won’t do it (and what the helper assumes)
Search terms like “lux to nits” are common, but lux and nits measure different things. To connect them, you must assume something about how a surface reflects/emits light.
The page includes a mini-helper for the most common simplifying assumption: an ideal diffuse (Lambertian) surface.
nits ≈ lux / π (π ≈ 3.1416) lux ≈ nits × π
What this means in plain language: if a surface sends light out evenly in all directions (Lambertian), then its luminance and the illuminance it produces follow the π relationship.
Rule-of-thumb table: lux ↔ nits under Lambertian assumption
| Illuminance (lux) | Approx luminance (nits) | How to use it safely |
|---|---|---|
| 100 | ≈ 31.8 | Good for intuition; not for calibration |
| 300 | ≈ 95.5 | Common office lighting range comparison |
| 500 | ≈ 159.2 | Typical bright office/task lighting |
| 1000 | ≈ 318.3 | Very bright task/retail lighting |
Candela → lux: only possible with geometry
“Candela to lux” requires distance because illuminance falls off with the inverse-square relationship (on-axis, simplified):
lux ≈ cd / distance² (distance in meters)
Example: a 100 cd source measured 2 m away gives roughly 100 / 2² = 25 lux on-axis. Real-world results also depend on beam angle and where you measure on the surface.
📊 Examples with numbers you can sanity-check
Example 1: Convert 300 lux to footcandles
Compute: 300 lux ÷ 10.7639104167 ≈ 27.87 fc.
Interpretation: If your guideline is in footcandles but your meter reads lux, this is a clean, direct conversion (same quantity type).
Example 2: Convert 500 nits to lamberts
Compute: 500 cd/m² ÷ 3183.0988618 ≈ 0.1571 L.
Interpretation: Useful when older documentation uses lamberts but modern specs use cd/m².
Example 3: Lux → nits with Lambertian helper (approximation)
Compute: 500 lux ÷ π ≈ 159 nits.
Interpretation: This is a rough bridge between room lighting (lux) and perceived surface brightness (nits), only under the Lambertian assumption.
📌 Infographic & Visual Guide
Practical reading tip: if you’re converting for a project (office lighting, displays, AV), bookmark this page and the Unit Converters hub for related tools.
🌐 Use cases (and the logic mistakes that cause wrong conclusions)
Where this converter is genuinely useful
- Lighting design & audits: convert lux ↔ footcandle when guidelines and meters use different units.
- Display specs: compare panel brightness in nits (cd/m²) and translate older luminance references in lamberts.
- Photography & video: keep your notes consistent when a light meter, a client doc, and a fixture spec use different units.
Common “math/logic” mistakes (not UI mistakes)
- Mixing lux with nits as if they’re interchangeable: lux is incoming light; nits is outgoing light per area. Fix: use the lux↔nits helper only when Lambertian is an acceptable assumption.
- Assuming candela converts to lux without distance: intensity does not include how far you are from the source. Fix: use lux ≈ cd / distance² only for simplified on-axis estimates, and measure if it matters.
- Using one measurement point as “the room value”: illuminance can be uneven. Fix: measure at the task plane across multiple points and average.
Related hubs for planning projects
- Home & DIY tools can help when lighting changes are part of a renovation plan.
- Energy tools can help estimate cost or impact when you’re comparing lighting options.
- Data tools are handy if you’re working with measurement logs or calibration notes.
Last Verified: December 2025
❓ Frequently Asked Questions
Why can’t I convert lux directly to nits in the main converter?
Lux is illuminance (light arriving on a surface), while nits (cd/m²) are luminance (light leaving a surface). They are different quantities, so a direct 1:1 unit conversion is not physically defined without assumptions.
When is the lux ↔ nits helper reasonable to use?
Use it only as a rule-of-thumb when you assume an ideal diffuse (Lambertian) surface: nits ≈ lux/π and lux ≈ nits×π. It’s useful for quick intuition, not precise calibration.
What’s the exact relationship between lux and footcandle?
Both are illuminance. 1 footcandle = 10.7639104167 lux, and 1 lux = 0.09290304 footcandle.
What is a nit (cd/m²)?
A nit is luminance equal to 1 candela per square meter (1 cd/m²). It’s commonly used to describe display brightness.
How do lamberts relate to nits?
Lambert is a non-SI luminance unit. 1 lambert ≈ 3183.0988618 cd/m² (nits). So 1 nit ≈ 0.000314159 lamberts.
Can I convert candela (cd) to lux?
Not as a pure unit conversion. On-axis, illuminance can be estimated from intensity with geometry: lux ≈ cd / distance² (distance in meters). Beam angle and measurement position also matter.
Why does distance matter for cd → lux estimates?
Candela describes the source’s intensity in a direction, while lux is what arrives on a surface area. As you move farther away, the same light spreads over a larger area, so illuminance falls with the inverse-square relationship.
What’s the most common mistake with brightness specs?
Mixing up display luminance (nits, cd/m²) with room lighting illuminance (lux). A monitor can be 400 nits while the desk lighting might be 300 lux—those numbers aren’t directly interchangeable.
Where should I measure lux in a room or workplace?
Measure on the task plane (where the work happens), typically the desk or work surface, and average multiple points if lighting is uneven. Measuring too close to a lamp or at eye level can misrepresent actual task illuminance.
Is this converter suitable for compliance or safety-critical design?
The within-type unit scaling (e.g., lux↔footcandle, nit↔lambert) follows standard definitions, but the lux↔nits helper is approximate. For compliance, use calibrated meters and follow your applicable standards and local regulations.
Short disclaimer: This page is for educational use and practical planning. Conversions within the same quantity type follow standard unit definitions. Lux↔nits is approximate and assumes an ideal Lambertian surface; do not rely on it for precision calibration or safety-critical decisions.