120Hz Test

Press Start: ten seconds later you see the frames a second your browser draws, read against 120.

The rate you expect Opens on 120 Hz. Press Start.

What to look for

Press Start for a count of 10 s

120 Hz: the rate this page opens on

Strip, about 192 steps a crossing at 120

120 Hz · one frame every 8.3 ms

One frame lasts 8.33 ms, which is 1,000 divided by 120, and a ten-second count comes to about 1,200 frames. A count of 116.4 to 123.6 frames a second is read as a match.

Right now frames a second

This is the browser's rate. The monitor's own rate can be higher.

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What to watch
Run for

What to look for

What a count means with 120 picked

How the count is made at 120 Hz

Next step Now time your reactions on this screen

All 16 rates and readings

Rates to read the count against 5

  • 60 Hz: half of 120 One frame every 16.67 ms, twice the 8.33 ms of 120 Hz, and about 600 frames in ten seconds. Pick it when 60 is the rate you expect: a count of 58.2 to 61.8 is then a match, not a shortfall.
  • 90 Hz: three quarters of 120 One frame every 11.11 ms and about 900 frames in ten seconds. With 90 picked, a count of 87.3 to 92.7 is a match. With 120 picked, the same count is named as the rate of a 90 Hz screen.
  • 120 Hz: the rate this page opens on One frame lasts 8.33 ms, which is 1,000 divided by 120, and a ten-second count comes to about 1,200 frames. A count of 116.4 to 123.6 frames a second is read as a match.
  • 144 Hz: a fifth faster than 120 One frame every 6.94 ms, 1.39 ms shorter than at 120, and about 1,440 frames in ten seconds. The two bands do not touch: 120 ends at 123.6 and 144 begins at 139.7, so a count tells them apart.
  • 240 Hz: twice 120 One frame every 4.17 ms and about 2,400 frames in ten seconds. With 240 picked, a count of 120 is read as half the rate. With 120 picked, a count of 240 is named as the rate of a 240 Hz screen.
Show all 16 rates and readings (11 more)

What a count means with 120 picked 4

  • A count of 60 with 120 picked Sixty is exactly half of 120, so this one figure fits two cases the count cannot tell apart: a browser that stops at 60 frames a second, and a browser drawing on every second refresh. Run the count in a second browser and compare.
  • A match with 120 picked With 120 picked, a match is an average between 116.4 and 123.6 with the frames coming evenly, about 8.33 ms apart. A web page can report no more than this: the figure is what the browser drew, and the page cannot see the screen itself.
  • An uneven pace at 120 The pace is called uneven when fewer than nine frames in ten land within a quarter of the usual frame time, which at 120 Hz is 6.25 to 10.42 ms. The average can still read 120 while single frames run long and short.
  • Frames missing from a 120 count At 120 Hz a frame that takes longer than 12.5 ms, one and a half times the usual 8.33, is counted as missing. The result says so when six or more go missing in a ten-second count at 120. Fewer are passed over.

What to watch while it counts 3

  • Graph with its line at 8.33 ms One column a frame, as tall as the frame was long, with a line at the length of a frame of the rate picked: 8.33 ms for 120 Hz. A level trace on the line is an even 120. Nothing moves.
  • Lanes at 120, 60 and 30 Three blocks move at one speed. The top one is redrawn every frame, the middle one every second frame and the bottom one every fourth: with the browser at 120 that is 120, 60 and 30 frames a second, side by side.
  • Strip, about 192 steps a crossing at 120 A white bar crosses the picture in about 1.6 seconds, one step a frame: about 192 steps at 120 Hz, where 60 Hz gives about 96. Even frames leave an even comb of bars, and a frame that never came leaves a gap.

How the count is made at 120 Hz 4

  • 120 divides by 24 and by 30 120 is the smallest multiple 24 and 30 share. Film at 24 frames a second fits five refreshes to a frame and 30-frame video fits four, with nothing left over. Televisions in countries with 30-frame broadcasts took the rate up for that reason.
  • A count of 119.9 or 120.1 Either is 120. The time stamp a browser gives a page can be as coarse as 1 ms against a frame of 8.33 ms, so the page judges the average of the whole count and treats 116.4 to 123.6 as a match.
  • The first half second is left out Every count throws away its first half second, about 60 frames at 120 Hz, so a slow start after the press cannot pull the average down. The figure rests on the remaining nine and a half seconds, about 1,140 frames.
  • Keep the tab in front while it counts Most browsers pause the drawing of a page in a background tab, so the frames stop arriving the moment the tab is hidden. The page throws that count away and says so. Bring the tab back and press Start again.

How this list was compiled: Written for this page. Every frame time, frame count and band was worked out: a frame lasts 1,000 ms divided by the rate, a ten-second count comes to ten times the rate, and a match is the rate give or take 3 percent. That a browser draws in step with the display refresh rate as a rule, that most browsers pause the drawing of a page in a background tab, and that the time stamp a page is given has a minimal precision of 1 ms, is from https://developer.mozilla.org/en-US/docs/Web/API/Window/requestAnimationFrame. That 120 was chosen for televisions in countries with 30-frame broadcasts, as the least common multiple of 24 and 30, is from https://en.wikipedia.org/wiki/Refresh_rate. That Safari's setting to prefer page rendering updates near 60 frames a second is on by default on macOS, iOS and iPadOS is from WebKit bug 173434, https://bugs.webkit.org/show_bug.cgi?id=173434 (open, last changed 2026-05-19). All read 2026-10-06. The page counts how often the browser draws, which can be lower than the rate of the screen. Licence: own work

How it works

This 120Hz test counts the frames your browser draws for ten seconds and reads the average against 120. Anything from 116.4 to 123.6 frames a second is a match.

Read the full guide

A 120 fps test, read for you

1. Leave the tab in front until the ten seconds are up. 2. Read the line under the figure: a match for 120, a count of 60, or another rate by name. 3. To compare, change one thing, such as the browser, and count again.

Questions and answers

What does a 120fps test count on a 120 Hz screen?

Frames the browser draws. Hz is how often a screen refreshes, fps how many frames are drawn; a browser draws in step with the screen as a rule, so one count stands for both. A game's frame rate is separate: check it inside the game.

How do I test refresh rate at 120 Hz?

Press Start and wait ten seconds. A match means the browser drew at 120. A lower figure does not prove the screen is slower: the page counts what the browser draws, and a browser can run below the screen's own rate.

Why does my 120Hz screen refresh test show 60?

Some browsers hold pages to 60. Safari keeps page updates near 60 frames a second by default, so a 120 Hz screen can read 60 there. Run the count in another browser before you draw a conclusion.

Is 120 Hz twice as fast as 60 Hz?

In frames, yes: a new one every 8.33 ms against every 16.67 ms, so about 1,200 in ten seconds against 600. A count shows that the browser draws them. It cannot show how much smoother motion looks to you.

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