60Hz, 120Hz, 144Hz and 240Hz: turn refresh rate into refresh interval

Refresh rate is usually advertised as a large number in hertz. The practical time-domain version is easier to compare: how many milliseconds are available between refreshes? The conversion is simple, but it also shows why refresh rate is not the same thing as frame rate, pixel response time, or variable-refresh-rate quality.

Updated 27 August 2026 · BIPM and VESA source check

The conversion: refresh interval = 1000 ÷ refresh rate

The BIPM defines the hertz as the SI unit of frequency, with 1 Hz = 1/s. For a display refreshing at a fixed rate, the ideal interval between refreshes is therefore the reciprocal of that frequency. Converting seconds to milliseconds gives:

refresh interval in ms = 1000 ÷ refresh rate in Hz

For 60Hz, 1000 ÷ 60 = 16.666..., so the interval is about 16.67ms. For 240Hz, 1000 ÷ 240 = 4.166..., or about 4.17ms. This arithmetic is a timing conversion only. It does not measure the entire chain from a mouse click to a visible pixel change.

Why doubling the refresh rate halves the interval

The relationship is reciprocal, so doubling the frequency halves the time between refresh opportunities. Moving from 60Hz to 120Hz changes the interval from about 16.67ms to 8.33ms. Moving from 120Hz to 240Hz halves it again to 4.17ms.

This also exposes diminishing absolute time savings. The jump from 60Hz to 120Hz removes about 8.33ms from the refresh interval. The jump from 120Hz to 240Hz removes another 4.17ms. The percentage improvement is the same, but the number of milliseconds removed each time becomes smaller because the starting interval is already shorter.

Refresh rate is not the same as FPS

A display's refresh rate describes how often the display can present refreshes under a given mode. FPS describes how many frames a rendering system actually produces per second. The two numbers can match, but one does not guarantee the other.

For example, a 240Hz monitor still does not prove that a game will run at 240 frames per second. Rendering load, CPU and GPU performance, game settings, resolution, frame pacing, and synchronization behavior remain separate parts of the system. Likewise, a source producing fewer frames can still be connected to a display whose maximum refresh capability is higher.

VESA's Adaptive-Sync certification language is useful here because its logo value represents the maximum video frame rate achievable for Adaptive-Sync operation under the certification test conditions. That is more specific than treating the printed hertz number as a guarantee about every application.

Refresh interval is not pixel response time

A 240Hz interval of about 4.17ms does not mean the display's pixels automatically complete every gray-to-gray transition in 4.17ms. Refresh timing and pixel transition behavior are different measurements.

VESA's Adaptive-Sync Display compliance program tests them separately: the standard includes refresh-rate requirements as well as gray-to-gray response, overshoot and undershoot, frame-drop, flicker, and frame-rate-jitter criteria. That separation is a useful buying rule. A high refresh rate is one specification; motion behavior depends on additional panel and timing characteristics.

The same caution applies to a monitor box that advertises a very small response-time number. That number does not replace refresh rate, and refresh rate does not replace response-time testing. If motion performance matters, keep both measurements attached to their test conditions rather than collapsing them into one “speed” score.

Variable refresh rate changes the timing pattern

With a fixed refresh mode, the simple 1000 ÷ Hz calculation describes a regular ideal interval. Variable refresh rate changes when refreshes occur within the display's supported range so that display timing can follow source timing instead of repeating one fixed cadence.

That does not make the maximum refresh number meaningless. VESA's certification program still identifies maximum refresh performance, and its later Dual Mode update explicitly supports displays that can certify different maximum refresh rates at different resolutions. VESA gives the example of a display operating at 4K/144Hz and 1080p/280Hz.

The practical implication is that resolution and refresh rate may be linked modes rather than independent maximums. Before buying a monitor for a target combination such as 4K at high refresh, check that the exact resolution/refresh mode is supported instead of combining the highest resolution from one line of the specification sheet with the highest refresh rate from another.

The connection still has to carry the mode

A panel capable of a high refresh mode also needs a complete signal path that can deliver the chosen resolution, color format, bit depth, and refresh rate. The required bandwidth rises as more image data is sent. Depending on the mode, the path may rely on a higher-bandwidth DisplayPort or HDMI link, or on Display Stream Compression.

That is why refresh rate should be checked together with the connection specification. The DisplayPort cable-label guide, HDMI cable-category guide, and Display Stream Compression guide explain those separate parts of the compatibility chain.

A practical way to compare two refresh rates

1. Convert both rates to milliseconds. Use 1000 ÷ Hz so you can compare the actual timing difference rather than just the size of the headline number.
2. Check the exact resolution mode. Do not assume the maximum refresh rate applies at the panel's maximum resolution.
3. Separate monitor capability from game FPS. Decide whether your source can realistically produce frame rates that make use of the higher mode for the workloads you care about.
4. Check pixel-response evidence separately. A high hertz value is not a substitute for transition-time and overshoot behavior.
5. Verify the link path. Port version, cable capability, color depth, compression support, and any dock or adapter can affect whether the target mode is actually available.

What the arithmetic can and cannot tell you

The 1000 ÷ Hz conversion is exact for the ideal period associated with a stated frequency, so it is useful for comparing timing ceilings. It can tell you that 120Hz provides an 8.33ms interval, that 240Hz provides 4.17ms, and that doubling refresh rate halves the interval.

It cannot, by itself, tell you total end-to-end latency, motion clarity, pixel response, overshoot, frame pacing, GPU performance, or whether the selected cable and port can carry the mode. Those are separate measurements or compatibility conditions.

If you are comparing displays with different aspect ratios or pixel densities as well as different refresh rates, use the 16:9 versus 16:10 guide and pixel-density guide to keep physical shape and sharpness separate from timing.

Primary references

• BIPM — The International System of Units (SI), including the relation Hz = s⁻¹.
• VESA — launch of the Adaptive-Sync Display compliance standard and logo program, describing certification tiers and maximum video frame-rate logo values.
• VESA — Adaptive-Sync Display Dual Mode update, describing resolution-dependent maximum refresh certification such as 4K/144Hz and 1080p/280Hz.
• VESA Adaptive-Sync Display CTS r1.1, the public compliance test specification covering refresh, gray-to-gray behavior, frame drop, flicker, and timing criteria.