What are nits? Screen brightness, explained

A nit is the unit of screen brightness: one candela per square meter (1 cd/m²), roughly the light of one candle spread evenly over a square meter. The higher the number, the brighter the screen can glow.

When you shop for a laptop, a monitor or a TV, the nit rating tells you how well the screen copes with a bright room, and whether it can show the bright highlights of High Dynamic Range (HDR) video. On Apple Silicon Macs, brightness ranges from 500 nits on a MacBook Air to 1,600 nits for HDR highlights on a MacBook Pro.

What does a nit actually measure?

In optical physics, a nit measures luminance: the intensity of visible light emitted per unit of surface area in a specific direction. The term comes informally from the Latin word nitere, meaning “to shine.”

The nit is built on the candela (cd), one of the seven base units of the International System of Units (SI). A candela measures luminous intensity, roughly the light of an ordinary candle. A surface glowing with one candela for every square meter of its area has a luminance of 1 cd/m², or 1 nit.

Because modern backlit LCD and self-emissive OLED panels pack thousands of microscopic light-emitting elements into compact glass panes, consumer screens produce hundreds or thousands of nits. A smartphone screen shining at 1,000 nits outputs the equivalent surface intensity of one thousand candles concentrated into a square meter, creating enough punch to remain legible under direct noon sunlight.

Nits vs lumens: what is the difference?

People often confuse nits with lumens because both terms describe brightness, but they measure fundamentally different physical properties:

• Lumens measure luminous flux: This is the total volume of visible light radiated by a light source in every direction simultaneously. Lumens are used to rate light bulbs, studio strobes, and home theater projectors.
• Nits measure luminance: This is the perceived surface brightness of a display screen viewed from a specific angle, calculated per unit of area.

Picture a projector rated at 2,000 lumens. Aim it at a 120-inch screen and the light spreads over a large area: the picture looks fairly dim. Aim the same projector at a sheet of paper and the same light is squeezed into a small area: the paper glows blindingly bright. The lumens didn’t change; the nits did.

Lumens tell you how much raw light a lamp throws into a room. Nits tell you how bright a flat display looks when your eyes look straight at it.

Diagram

How bright is bright? Brightness in nits

1001,00010,000

• SDR whiteWhat ordinary video is mastered for (ITU-R BT.1886)100 nits
• HDR reference whitePaper, faces and subtitles in HDR (ITU-R BT.2408)203 nits
• MacBook Air, iMacTheir full brightness: HDR is fitted inside it500 nits
• HDR mastering, commonMost HDR films are graded on 1,000-nit monitors1,000 nits
• MacBook Pro XDR peakHighlights in HDR video (1,000 nits full screen)1,600 nits
• HDR mastering, high endSome films are graded on 4,000-nit monitors4,000 nits
• PQ ceilingThe most HDR10 and Dolby Vision can describe10,000 nits

How many nits do you need for good screen brightness?

The ideal brightness for a screen depends heavily on your physical environment and the kind of content you are viewing:

• 100 nits (SDR Studio Reference): Standard Dynamic Range mastering suites calibrate reference monitors to 100 nits under Recommendation ITU-R BT.1886. In a dark room with controlled ambient lighting, 100 nits provides comfortable contrast without straining human vision.
• 250 to 300 nits (Budget Laptops & Office Monitors): Baseline monitors produce roughly 250 to 300 nits. This level is sufficient for indoor office work under fluorescent lighting, but struggles when placed next to an open window.
• 400 to 500 nits (Premium Laptops & Tablets): The Apple MacBook Air, 24-inch iMac, and modern premium ultrabooks deliver 500 nits. This brightness easily overcomes harsh indoor reflections and allows comfortable reading in bright coffee shops or shaded outdoor patios.
• 800 to 1,000 nits (Outdoor Mobile Screens): High-end smartphones push 800 to 1,000 nits in high-brightness mode so maps, text messages, and camera viewfinders remain legible under blazing sunlight.
• 1,000 to 1,600+ nits (HDR displays): For HDR video to show bright, sparkling highlights, a screen needs to reach around 1,000 nits in small areas, with deep blacks around them (OLED, or mini-LED with local dimming).

How many nits are required for true HDR?

One of the greatest points of consumer frustration in modern display marketing is the proliferation of entry-level monitors branded with HDR badges despite lacking the luminance power to display HDR video.

VESA DisplayHDR 400 monitors, for instance, are only required to reach a peak brightness of 400 nits. Because standard SDR laptop displays already hit 400 to 500 nits, a 400-nit screen offers zero additional dynamic range. When fed an HDR signal, a 400-nit display must compress highlight information, frequently causing dark movie scenes to look dimmer and more washed out than the standard SDR version.

True High Dynamic Range is built on the Perceptual Quantizer transfer curve (SMPTE ST 2084), which scales up to 10,000 nits. Hollywood mastering suites grade modern blockbuster movies on dual-cell LCD and OLED mastering monitors calibrated to 1,000 nits (such as the Sony BVM-HX3110) or 4,000 nits (such as the Dolby Pulsar).

In an HDR film grade:

1. Diffuse white sits at 203 nits: Under Report ITU-R BT.2408, standard indoor elements, white paper, and actor skin tones are anchored around 203 nits.
2. Highlights utilize 1,000+ nits: All the extra luminance above 203 nits is dedicated exclusively to specular highlights: chrome glints, lightning, streetlights at night, and explosions.

A display comes closest to what the colorist saw when it combines a peak of 1,000 nits or more with deep blacks, from OLED or from fine local dimming.

Full-screen sustained vs peak brightness: why numbers mislead

When evaluating display specifications, pay close attention to whether a manufacturer is quoting full-screen sustained brightness or peak brightness.

• Full-screen sustained brightness: The maximum luminance the display can maintain continuously across 100 percent of the screen area displaying solid white. Sustained brightness is constrained by electrical power draw and thermal heat dissipation.
• Peak brightness: The maximum luminance the display can generate momentarily across a small window—typically 10 percent or less of the panel surface.

For example, a high-end OLED television might advertise a peak brightness of 1,300 nits. However, if the entire screen displays a white snowfield in a ski documentary, an internal safeguard called the Automatic Brightness Limiter (ABL) dims the panel down to 200 or 250 nits to prevent overheating and panel degradation.

In contrast, Apple’s Liquid Retina XDR displays on 14-inch and 16-inch MacBook Pro models provide an exceptional 1,000 nits of sustained full-screen luminance for HDR content, alongside a 1,600-nit peak for highlights.

Diagram

Mac Display Peak Luminance Compared

• MacBook Air (13/15-inch)500 nits
• Studio Display (27-inch)600 nits
• Studio Display XDR (peak HDR)2,000 nits
• MacBook Pro XDR (Sustained)1,000 nits
• MacBook Pro XDR (Peak HDR)1,600 nits

How bright is a Mac screen?

Apple Silicon Macs feature distinct display technologies tailored to different workflows:

MacBook Air (13-inch and 15-inch)

The MacBook Air features an edge-lit IPS LCD display rated at 500 nits. It does not have local dimming zones and cannot boost highlights beyond 500 nits. When playing HDR content, macOS decodes the format but tone-maps the signal into the 500-nit SDR color volume.

MacBook Pro 14-inch and 16-inch (Liquid Retina XDR)

The flagship MacBook Pro models feature mini-LED backlights containing over 10,000 diodes arrayed into more than 2,500 local dimming zones. Standard SDR desktop tasks run at up to 600 nits (and up to 1,000 nits outdoors on M4 models). When playing HDR content, the panel unlocks 1,000 nits of sustained full-screen brightness and up to 1,600 nits of peak highlight luminance.

iMac (24-inch)

The 24-inch iMac incorporates a 4.5K Retina display delivering 500 nits of SDR brightness. Like the MacBook Air, it relies on edge LED lighting without local dimming zones.

Apple Studio Display (27-inch 5K)

The standalone Studio Display provides 600 nits of SDR brightness. It is an expansive, color-accurate P3 monitor for creative work, but it lacks mini-LED local dimming and does not support HDR highlight headroom.

Apple Studio Display XDR (27-inch 5K)

Apple’s newer Studio Display XDR (27-inch 5K) is an HDR display: a mini-LED backlight with 2,304 dimming zones, up to 1,000 nits for SDR and 2,000 nits peak for HDR, at up to 120 Hz (Apple’s specs).

Apple Pro Display XDR (32-inch 6K)

The Pro Display XDR features 576 full-array local dimming zones, outputting 500 nits for SDR tasks, 1,000 nits of sustained full-screen XDR luminance, and 1,600 nits of peak highlight luminance.

How macOS uses nits dynamically with EDR headroom

On macOS, HDR brightness is not a fixed switch. Apple’s Extended Dynamic Range (EDR) works with headroom: the screen’s peak brightness divided by the brightness of white right now.

In EDR, a value of 1.0 represents standard SDR white, determined by your manual brightness slider. On a MacBook Pro Liquid Retina XDR screen with a 1,600-nit hardware ceiling:

• With white at 500 nits, HDR highlights can be 1,600 ÷ 500 = 3.2 times brighter than white.
• Lower the brightness until white sits at 100 nits, in a dim room, and they can be 1,600 ÷ 100 = 16 times brighter.

Try it

Why HDR gets brighter when you dim a MacBook Pro

MacBook Pro (XDR)MacBook Air, iMacHDR monitor (600 nits)

White and everything belowHDR headroom

3.2× HDR highlights can be 3.2 times brighter than white.

Screen brightness (white)

500 nits

Lowering your screen brightness makes HDR highlights stand out more because the mini-LED backlight maintains its 1,600-nit physical ceiling for video highlights while dropping the surrounding desktop interface to a restful 100 nits.

How to optimize your display brightness for movies

To get the most impactful movie-watching experience on your Mac:

1. Avoid blasting SDR brightness in dark rooms: Cranking your brightness keys to maximum raises SDR white, shrinking your display’s relative HDR headroom and causing eye fatigue.
2. Watch in subdued lighting: Minimizing ambient room reflections lets you lower baseline brightness, unlocking the full 1,600-nit highlight capability of XDR screens.
3. Check the battery setting: in System Settings › Battery › Options, “Optimize video streaming while on battery” plays HDR streams as SDR to save power. Turn it off if you want HDR on battery.
4. Choose the right picture style: When watching films mastered at 4,000 nits on a dimmer display, use a player like MacLC that offers ITU-R BT.2390 tone-mapping presets to avoid clipped highlights.

Understanding nits removes the mystery from display specifications. To see how your specific Mac model handles high-luminance video, read our full breakdown on does my Mac support HDR, or discover how macOS composites light in our explainer on Apple EDR and XDR.