A refresh rate of N Hz means the screen redraws N times a second — once every 1000 ÷ N milliseconds. That makes 60Hz 16.67ms, 144Hz 6.94ms and 240Hz 4.17ms. What falls out immediately is that the bigger the number gets, the less time each step saves. Moving from 60 to 144 cuts 9.73ms; moving from 144 to 240 cuts only 2.78ms.
And the higher the refresh rate, the more the bottleneck shifts from the panel to the cable. A 4K 240Hz 10-bit signal carries roughly 59.7 gigabits per second of pure video data — more than twice the 25.92Gbps of usable bandwidth in DisplayPort 1.4.
Refresh rate, converted to milliseconds
Samsung's monitor guide defines refresh rate as "how many times per second the monitor refreshes the image," treating 60Hz as the standard for documents and web use and 144Hz and above as the gaming band. Convert that split into time and you can see what each step actually buys.
| Refresh rate (Hz) | Frame interval (ms) | Saved vs 60Hz (ms) | Saved vs previous step (ms) |
|---|---|---|---|
| 60 | 16.67 | — | — |
| 75 | 13.33 | 3.34 | 3.34 |
| 120 | 8.33 | 8.34 | 5.00 |
| 144 | 6.94 | 9.73 | 1.39 |
| 165 | 6.06 | 10.61 | 0.88 |
| 180 | 5.56 | 11.11 | 0.50 |
| 240 | 4.17 | 12.50 | 1.39 |
| 360 | 2.78 | 13.89 | 1.39 |
| 480 | 2.08 | 14.59 | 0.70 |
Going all the way from 60Hz to 480Hz saves 14.59ms in total — and 8.34ms of that, 57% of everything available, comes from the single 60→120 step. Past 120Hz, every remaining step splits the leftover 6.25ms. The 1.39ms gained from 240 to 360 is smaller than the 3.34ms gained from 60 to 75.
The table computes physical refresh interval only. Perceived smoothness also depends on pixel transition speed and sample-and-hold persistence. The pixel side is a separate calculation, covered in where GtG and MPRT figures diverge. The relationship is simple enough, though: if 240Hz gives you a 4.17ms frame interval but pixels take 5ms to switch, the transition is still unfinished when the next frame arrives, and smear remains.
The refresh number grows while the time it saves shrinks — 60 to 144 buys 9.7ms, but 144 to 240 buys only 2.8ms.
How much GPU does 240Hz actually need?
Refresh rate is a ceiling, not a guarantee. For a 240Hz monitor to refresh 240 times, the graphics card has to finish a frame every 4.17ms. At an average of 120fps the real interval is 8.33ms — the same timeline as a 120Hz panel. Raise the refresh rate without the frames to fill it and all you gain is a spec sheet line.
Variable refresh rate exists to handle the gap. The same Samsung guide describes G-Sync and FreeSync as matching "the monitor's refresh rate to the GPU output" to eliminate tearing and stutter. Buy a 240Hz panel and sit at 150fps, and what you actually gain is not 240Hz but the smoothness VRR recovers.
The most-cited evidence for perceived benefit also needs its conditions stated. BenQ ZOWIE quotes an NVIDIA study finding a 53% increase in K/D ratio among FPS players who switched to 240Hz monitors — but that is observational data on a group invested enough in gaming to buy high-refresh hardware in the first place. Reading it as a controlled before-and-after on the same players overstates it.
The cable runs out first
Video data per second is horizontal pixels × vertical pixels × refresh rate × bits per pixel. RGB 8-bit is 24 bits per pixel; 10-bit is 30. On the supply side, TFTCentral's figures are the reference. DisplayPort 1.4's HBR3 runs 8.10Gbps per lane across 4 lanes for 32.40Gbps raw, but 8b/10b encoding leaves 25.92Gbps usable. DisplayPort 2.1 switches to 128b/132b for 96.7% efficiency: UHBR10 delivers 38.69 of 40Gbps, UHBR13.5 delivers 52.22 of 54Gbps, and UHBR20 delivers 77.37 of 80Gbps. HDMI 2.1's raw figure is 48Gbps.
Run the formula across resolution and refresh combinations and the wall becomes a number.
| Resolution · refresh | Color depth | Raw video data (Gbps) | HBR3 (25.92Gbps) | UHBR20 (77.37Gbps) |
|---|---|---|---|---|
| FHD 1920×1080 · 240Hz | 8-bit | 11.94 | Ample | Ample |
| QHD 2560×1440 · 240Hz | 8-bit | 21.23 | Fits | Ample |
| QHD 2560×1440 · 240Hz | 10-bit | 26.54 | Over | Ample |
| 4K 3840×2160 · 120Hz | 8-bit | 23.89 | Fits | Ample |
| 4K 3840×2160 · 120Hz | 10-bit | 29.86 | Over | Ample |
| 4K 3840×2160 · 240Hz | 8-bit | 47.78 | Over | Ample |
| 4K 3840×2160 · 240Hz | 10-bit | 59.72 | Over | Fits |
| 4K 3840×2160 · 480Hz | 10-bit | 119.44 | Over | Over |
Real transmission adds a few percent of blanking overhead, so these are floor values. Allow for that and the results line up exactly with TFTCentral's summary that HBR3 tops out uncompressed at 4K 120Hz and 1440p 240Hz — both of which land just under 25.92Gbps at 8-bit.
The workaround when bandwidth runs short is DSC (Display Stream Compression), a roughly 3:1 visually lossless scheme that squeezes 4K 240Hz down a HBR3 or HDMI 2.1 pipe. Sending it uncompressed instead requires UHBR20, which TFTCentral lists as driving 8K 60Hz, 4K 240Hz and 1440p 480Hz without compression. In shipping products, MSI's 27-inch 4K 240Hz QD-OLED carries DisplayPort 2.1a UHBR20.
Cable grade matters too. UHBR20 requires a DP80-certified cable; plug in a previous-generation DisplayPort cable and the link drops back to UHBR13.5 or HBR3. The same gap between a headline figure and an achievable one shows up in how Thunderbolt 5 and USB4 both claim 80Gbps.
Which combination fits
- Competitive FPS or rhythm games are the main use, and the GPU can genuinely hold 200fps or more with settings turned down
- Resolution stays at FHD or QHD — bandwidth headroom is large enough that ports and cables barely constrain anything
- Panel GtG response is comfortably shorter than the 4.17ms frame interval
- Documents, web and video are the main use — 60→120 already captures 57% of the total available improvement
- The goal is 4K at high settings but average frame rates sit around 100fps. The GPU is the limit before the panel is
- You want 10-bit HDR output without DSC in the path and have no UHBR20 port
The order to check before buying is frames, then ports, then cable. Decide what average frame rate your target games actually produce, pick a refresh rate that frame rate can fill, then use the table above to compute the bandwidth your resolution, refresh and color depth require and confirm the GPU output and cable grade can carry it. Reverse the order and you end up feeding 120fps to a 240Hz panel, or a legacy cable to a UHBR20 monitor.