What is a refresh rate?
A refresh rate is how many times per second your display draws a new image, measured in hertz (Hz). A 60Hz monitor paints 60 fresh images every second. A 144Hz one paints 144. How smooth a scroll feels, how fluid a mouse pointer looks, how current the picture is when you flick your wrist in a shooter — all of it follows from that one number.
The number matters because it sets a hard floor on how stale the image in front of you can be. At 60Hz, a frame sits on screen for 16.7 milliseconds before anything can replace it. At 144Hz that drops to 6.9 milliseconds, and at 240Hz to 4.2. Nothing your computer does can deliver news to your eyes faster than the panel is willing to redraw.
Here's the catch, and it's the reason this page exists: refresh rate is a property of the display and the graphics pipeline feeding it — not of the box the monitor came in. A 165Hz panel connected with a cable that can't carry 165Hz at your resolution will quietly run at 60 and never mention it. A graphics driver update can reset the display mode overnight. Windows and macOS both report the rate they asked for, which is the rate they believe is configured, not the rate frames are actually arriving at. The gap between those two things is what the Refresh Rate Test measures. If the question in your head is what is my refresh rate, actually — rather than what the settings panel claims it is — that gap is the whole answer.
How to use the Refresh Rate Test
- Open the page on the display you want to check. The test starts on its own — there's no button to hunt for and nothing to configure.
- Leave the tab in front for about five seconds. The frames right after a page load are noisy, so the first ten are thrown away before anything counts toward the result.
- Read the big number. If the measurement lands within 2% of a rate panels are actually sold at, it snaps to that rate and tells you so: Matches a standard 144Hz panel.
- Check the jitter figure beside it. Near zero means a steady panel. A wide spread means frames were being dropped while the test ran — which is the difference between "my monitor is at 60" and "my browser couldn't keep up".
- Press Test again for another run, or switch the window to 3 or 10 seconds. Use 10 when you suspect something on the machine is intermittently stealing frames.
Six numbers sit under the headline: measured rate, jitter, frame time in milliseconds, slowest, fastest, and how many frames were sampled. They're there so you can tell a real reading from a bad one without trusting a single averaged figure.
Most pages that measure one fact about your hardware make you work for it first — a utility to download and install, a signup so the site can "save your results", a second test parked behind an upgrade, or half a megabyte of article stacked above the thing you came for. This measurement is a few hundred timestamps and one division. It runs the moment the page loads, it's free, and there's nothing to install or sign up for.
How the measurement works
Browsers hand every page a callback immediately before each frame is sent to the screen, along with a high-resolution timestamp. Collect a few hundred of those timestamps, look at the gaps between them, and you have the frame interval. Invert it and you have the refresh rate.
Refresh rate (Hz) = 1000 ÷ median frame interval (ms)
A five-second run of the Refresh Rate Test on a 144Hz panel collects roughly 730 timestamps. The first 10 are discarded as warm-up, which leaves 719 intervals. Sort them and take the middle one: 6.944 ms. Divide: 1000 ÷ 6.944 = 144.0 Hz. That's inside 2% of 144, so the headline snaps to 144 Hz and the copy button gives you the full line — 144 Hz (measured 144.0 Hz, jitter ±0.0 Hz). The same run on a 60Hz display collects about 310 timestamps, yields 299 intervals with a median of 16.667 ms, and reads 60 Hz.
Why the median, and not the average
Because one bad frame ruins an average. Take a clean 60Hz run of 300 frames and make a single frame arrive 120 ms late, the way a garbage-collection pause or a background process would. The median interval doesn't move — it's still 16.667 ms, so the headline still reads 60 Hz, which is the truth about the panel. The stall isn't swept under the rug, though: the Slowest figure drops to 8.3 Hz, which is exactly where information about a dropped frame belongs.
The jitter figure works the same way. It's half the spread between the 10th and 90th percentile intervals, not the distance between the two most extreme frames — so one hitch reads as a hitch, while a genuinely unstable display reads as unstable.
Standard refresh rates and their frame times
The headline only snaps to a rate displays are really sold at, and only when the measurement lands within ±2% of it. Everything else is shown raw. Here's the full snapping table:
| Rate | Frame time | Snaps from | Where you'll see it |
|---|---|---|---|
| 60 Hz | 16.667 ms | 58.8–61.2 Hz | Office monitors, most laptops, every TV-adjacent panel |
| 75 Hz | 13.333 ms | 73.5–76.5 Hz | Budget monitors sold as "above 60" |
| 90 Hz | 11.111 ms | 88.2–91.8 Hz | Mid-range phones, some VR headsets |
| 100 Hz | 10.000 ms | 98–102 Hz | Ultrawides, overclocked 60Hz panels |
| 120 Hz | 8.333 ms | 117.6–122.4 Hz | Current consoles, iPad and iPhone ProMotion |
| 144 Hz | 6.944 ms | 141.1–146.9 Hz | The default gaming monitor for a decade |
| 165 Hz | 6.061 ms | 161.7–168.3 Hz | 144Hz panels with headroom, sold a tier up |
| 180 Hz | 5.556 ms | 176.4–183.6 Hz | Newer budget gaming panels |
| 240 Hz | 4.167 ms | 235.2–244.8 Hz | Competitive esports monitors |
| 360 Hz | 2.778 ms | 352.8–367.2 Hz | High-end esports panels |
| 500 Hz | 2.000 ms | 490–510 Hz | The current ceiling on consumer displays |
Two more rates — 170Hz and 280Hz — are in the snapping list but left out above to keep the table readable. Notice how quickly the gains shrink down the column. Moving from 60Hz to 120Hz cuts 8.3 ms off how long a frame lingers. Going from 240Hz to 360Hz buys 1.4 ms. The first upgrade is one most people can see; the last one is bought by players who need it and measured by everyone else.
The tolerance is deliberately tight. A monitor sold as 144Hz that measures 141.5 Hz snaps to 144, because that's measurement noise. One that measures 122.5 Hz does not snap to 120 — it's 2.08% off, just outside the window — so you get the raw figure instead of a comfortable-looking round number that hides a real problem.
When the number isn't what you expected
A reading that doesn't match the box usually falls into one of three buckets, and the tool labels each one rather than printing a single confident number.
A non-standard rate
Frames arriving 10.288 ms apart work out to 97.2 Hz. That's not within 2% of anything on the list, so the headline reads 97.2 Hz with a note that it isn't a standard rate — and it deliberately doesn't round up to 100. Two innocent explanations cover most cases: the display is overclocked on purpose, or something on the machine is capping frames, like a power-saving mode or a frame limiter.
A variable-refresh display
Adaptive panels — ProMotion, VRR, FreeSync, G-Sync — change rate on the fly to save power. Measure one and the intervals genuinely alternate: 8.333 ms, then 16.667 ms, then back. Collapsing that to a single figure gives 120.0 Hz with jitter of ±30.0 Hz — a number the display never actually sits at. Once jitter passes ±10%, you get a range instead — 60–120 Hz, labelled as adaptive refresh. That's the honest answer, and it's one most refresh rate checkers get wrong by reporting a single averaged value.
A voided run
Browsers throttle the frame clock to roughly one frame per second in a tab you can't see, to save battery. Switch tabs mid-run and the Refresh Rate Test throws the samples away and asks you to start over. The alternative would be reporting 1Hz and making a healthy monitor look broken.
Fewer than about a dozen usable frames and you'll see Measuring… rather than a number. No zero, no NaN, no half-formed reading that changes under you — the tool would rather show nothing than show something wrong.
Related screen and timing tools
Refresh rate is one of several things worth checking on a new display. The dead pixel test cycles solid colours full-screen so stuck and dead subpixels have nowhere to hide — the first thing to run on a monitor that's still inside its return window. The PPI calculator works out pixel density from resolution and diagonal size, which is what actually determines whether text looks crisp at your viewing distance, and the aspect ratio calculator handles the resolution arithmetic when you're matching a second monitor to the one you already own.
On the timing side, the reaction time test measures how fast you respond to a colour change — and your refresh rate is baked into that score, since a 60Hz panel can add up to 16.7 ms of display latency before you've even seen the cue. The click speed test counts clicks per second the same way. If you're chasing smoothness over a network rather than on the panel, the bandwidth calculator converts between transfer rates and times.
Frequently asked questions
Is refresh rate the same as FPS?
No, though they're related. Refresh rate is how often the display can draw; frames per second is how many images the software actually produces. A game running at 200 fps on a 60Hz monitor still shows you 60 images a second — the rest are discarded. The Refresh Rate Test measures how fast the browser is getting frames onto the panel, which under normal conditions equals the display's rate, because the browser is synchronised to it.
I have two monitors. Which one does this measure?
Whichever display the browser window is on. Move the window to the other monitor and press Test again; the screen refresh rate test re-runs against whatever panel the window is sitting on. This trips people up on laptops docked to an external screen, where the built-in display and the external one often run at completely different rates.
Can I check the refresh rate on my phone or tablet?
Yes, the test works the same way on mobile browsers. Expect more variation than on a desktop: many phones with 90Hz or 120Hz screens drop to 60Hz to save battery, throttle when they get warm, or use an adaptive panel that reports as a range. A result that moves between runs on a phone is usually the phone being clever, not a fault.
Why does it say 59.9 Hz instead of exactly 60?
Plenty of display modes run at 59.94Hz rather than a clean 60 — a leftover from NTSC colour television that never fully went away. The raw measurement shows it, and since 59.94 is well within 2% of 60, the headline snaps to 60 Hz. A measured figure a fraction under the round number is normal and not worth chasing.
Can I check my refresh rate without a test page?
You can check what it's set to. On Windows, that's Settings → System → Display → Advanced display. On macOS, System Settings → Displays. Both show the mode the operating system has selected, which is the number that's usually right and occasionally a lie — a cable that can't carry the bandwidth, or a monitor plugged into motherboard video instead of the graphics card, produces a settings panel that says 144 and a screen running at 60. Measuring frames is how you tell the two apart.
Does my browser or window size change the result?
Window size doesn't — the display refreshes at the same rate whether the window fills the screen or a corner of it. The browser can matter, but usually only when something is going wrong: a loaded machine, a heavy extension, or a page recording in the background will cause dropped frames, and those show up as jitter rather than as a different headline number. If you see a low reading with wide jitter, close everything else and run the monitor refresh rate test again before blaming the panel.