Monitor Gamma Test
Find the bar where the centre patch matches its surround to read your display gamma, compare it with the 2.2 sRGB target, and check red, green and blue separately for a mid-tone colour cast.
Gamma chart
Each bar is a horizontal linepattern, one device pixel on and one off, around a solid patch. Half the pixels are full on and half are black, so the pattern averages to halfway between black and full on at any gamma. The patch is the 8-bit level for that bar. Sit about an arm's length back, or squint, until the pattern turns flat, then pick the bar where the patch disappears. That bar's number is the gamma to record. The page does not measure light.
- 1.8 matches: mid-tones are too bright and shadows look grey.
- 2.0 matches: a little lighter than the sRGB target.
- 2.2 matches: the sRGB target for the web, Windows and most games.
- 2.4 matches: darker mid-tones, in the BT.1886 range for a dim room.
- 2.6 matches: mid-tones are too dark and shadow detail is crushed.
Pixel ratio 1.00: one device pixel on, one off, at this screen's native pixels, not one CSS pixel.
Numbers under each gamma are the 8-bit level of the solid patch (255 × 0.5^(1/γ)). Click a bar or its button to record it. If the patch looks brighter than every surround, your gamma is below 1.8; darker than every surround means above 2.6.
Drag until the centre patch vanishes into the pattern, then record the value.
Your result
Pick a bar on the grey chart to get a verdict against the 2.2 target.
Test red, green and blue too to check for a colour cast in the mid-tones.
How display gamma works
What gamma is
Gamma is the curve between the signal a monitor receives and the light it puts out. Black and white stay fixed; gamma decides how bright everything in between looks. With gamma 2.2, code 128 emits about 22% of full brightness, and code 186 is the nearest level to half the light. This test uses that: half the pixels in the surround are full on and half are black, so the average is halfway between black and full on at any gamma. The gamma of the patch that matches it is the curve your screen follows.
2.2 or 2.4?
The web, Windows, macOS and nearly all games are mastered for sRGB, which is very close to gamma 2.2, so 2.2 is the right target for a normal room. Film and TV grading uses BT.1886, roughly 2.4, because a darker curve looks correct in a dim room. A reading of 1.8 to 2.0 means a washed-out picture with grey shadows; 2.5 or more means harsh contrast and crushed shadow detail. Check the ends of the range as well with the black level test and white level test.
How to adjust it
Start with the monitor's own menu: most have a gamma setting (often labelled 1, 2, 3 or 1.8 / 2.2 / 2.6) or an sRGB mode. Turn off dynamic contrast and "black equaliser" style features, which bend the curve. If the menu has nothing, the GPU control panel (NVIDIA, AMD or Intel) has a gamma slider. A per-channel mismatch usually comes from the colour temperature or RGB gain settings. Re-run the grey chart after every change.
How accurate is this?
It is an eyeball check, good to about ±0.1 on a well-set screen. Viewing angle shifts gamma a lot on TN and VA panels, so look straight at the chart. Some panels smear alternating lines, which is why the checkerboard option exists. Browser colour management and night-light modes are part of the chain being measured. A spec sheet that claims "factory calibrated" is worth checking this way, but for real accuracy use a hardware colorimeter.
Related tools
- Black Level Test: see whether near-black shades are crushed or lifted.
- White Level Test: check the brightest shades are not clipped.
- Color Range Test: spot banding and a limited vs full RGB range mismatch.
- Display Test: a full set of monitor test patterns in one place.
Frequently asked questions
What does gamma 2.2 mean?
Gamma is the curve from the number a monitor receives to the light it emits. Black and white stay fixed, and gamma sets the mid-tones. At gamma 2.2, code 128 emits about 22% of full brightness, and code 186 is the nearest level to half the light. The web, Windows, macOS and most games are mastered for sRGB, which sits very close to 2.2, so 2.2 is the usual target in a normal room. 2.4 is the darker BT.1886 curve used for film and TV in a dim room.
How do I read the gamma chart?
Each bar is a pattern with half its pixels full on and half black, so the average light is halfway between black and full on no matter the gamma. The solid patch in the middle is the 8-bit level for that bar, 255 × 0.5^(1/γ): 174 at 1.8, 180 at 2.0, 186 at 2.2, 191 at 2.4 and 195 at 2.6. Pick the bar where the patch disappears into the surround. A match on 1.8 means mid-tones are too bright; 2.2 is the sRGB target; 2.4 suits a dim room; 2.6 means mid-tones are too dark. If the patch is brighter than every surround, gamma is below 1.8. If it is darker than every surround, gamma is above 2.6. The page records the bar you pick. It does not measure the screen on its own.
Does zoom or viewing distance change the match?
Yes. Use 100% browser zoom (Ctrl or Cmd + 0) and sit about an arm's length back, looking straight at the chart. Squinting or stepping back helps the pattern turn into a flat tone. A pixel ratio that is not a whole number, such as 125% or 150% scaling, can resample the pattern and skew the match. The chart is drawn one device pixel on and one off, but a fractional ratio can still blur it. TN and VA panels also shift gamma when you look from the side.
Is this a colorimeter?
No. A colorimeter measures light with a sensor. This page only draws a chart and stores the gamma of the bar you choose. Treat it as an eye check, about 0.1 either way when the pattern is sharp. For a real calibration, use a hardware colorimeter.
Why test red, green and blue as well as grey?
The grey bar is the gamma reading. Red, green and blue repeat the same pattern on one channel. If those three results disagree, mid-greys can take on a colour cast, often from colour temperature or the monitor's RGB gain rather than the gamma preset.
What if my gamma is not 2.2?
Start with the monitor menu: a gamma preset (often 1.8, 2.2 or 2.6) or an sRGB mode. Turn off dynamic contrast and black-equaliser options, which bend the curve. If the menu has no gamma control, the GPU panel from NVIDIA, AMD or Intel has a gamma slider. Run the grey chart again after each change. A 2.4 result can be right in a dark room and too dark for office and web work.
Should I use lines or the checkerboard?
Both patterns are half on and half off, and both use the same patch levels. Some panels smear thin horizontal lines, so the checkerboard is there as a second view. Use whichever pattern turns into an even tone when you step back. If the two patterns point at different bars, trust the one that looks smoother, and do not treat either as a meter reading.