Response time and input lag are two of the most-quoted gaming monitor specs and two of the least-understood. Manufacturers advertise the lower of the two as the headline number and frequently stay silent on the other. Reviewers measure them with different tools and methodologies, which produces apples-to-oranges comparisons. This guide walks through what each spec means, how it is measured, what affects each one, and which matters for the way you play in 2026.
Response time and input lag are different things
Response time measures how fast a single pixel changes from one color to another. The standard unit is gray-to-gray (GtG), measured in milliseconds, between a defined start and end gray level. A monitor advertised at 1 ms GtG can theoretically transition any pixel from one gray to another within one millisecond.
Input lag measures the delay between a signal arriving at the monitor (from the GPU, from a button press traveling through the PC stack) and the corresponding pixel actually changing on screen. This includes the monitor’s internal signal processor, scaler, and any post-processing the panel applies before the image is drawn.
Total click-to-pixel latency is response time plus input lag plus everything that came before the monitor in the chain. The two monitor specs add. A 1 ms GtG panel with 25 ms of input lag has worse total latency than a 4 ms GtG panel with 6 ms of input lag.
How response time is measured (and why GtG vs MPRT matters)
Gray-to-gray is measured with an oscilloscope or photodiode reading the pixel transition between two defined gray levels (typically RGB 50 to RGB 200, or some manufacturer-specific equivalent). The result depends heavily on which transition is measured. Manufacturers cherry-pick the fastest transition for the headline number; reviewers typically report average and worst-case figures.
Moving Picture Response Time (MPRT) is a different measurement. It captures how long a pixel remains “on” within a given frame, which determines how much sample-and-hold blur the eye perceives during motion. A 1 ms GtG monitor can still have a 5 ms MPRT if the panel does not strobe or black-frame insert between refreshes. Manufacturers sometimes report MPRT as their 1 ms claim, which is a different (and less useful) spec.
Honest specs typically include both. If a panel lists only one number, assume the other is worse than the headline.
How input lag is measured
Input lag testing usually involves a high-speed camera filming a mouse click and the corresponding screen update at 1,000 fps or faster, then counting frames between the two events. Tools like the Leo Bodnar lag tester, NVIDIA LDAT, and the OSRTT do this with hardware precision down to single milliseconds.
The monitor’s contribution to total lag varies widely. A panel optimized for competitive play (Asus ROG Swift PG27AQDP, LG UltraGear 27GR95QE, BenQ ZOWIE XL2566K) lands between 1 and 5 ms of processing delay. A TV-style “gaming” monitor with image processing on can sit at 20 to 50 ms even at high refresh rates. The same panel with image processing off and game mode on usually drops to single digits.
The settings that wreck input lag
Most monitors ship with image-enhancement features that add latency:
- Motion smoothing or “soap opera” interpolation, 8 to 25 ms
- Dynamic contrast and dynamic brightness, 2 to 8 ms
- AI upscaling and AI image enhancement, 4 to 12 ms
- HDR processing at lower-end monitors, 2 to 6 ms
- Local-dimming algorithms on FALD displays, 3 to 8 ms
- Non-native resolution requiring scaler, 4 to 15 ms
Game mode in a monitor’s OSD typically disables most of these in one button press. The cost is visual processing the panel might otherwise do; the gain is real input-lag reduction.
OLED vs fast IPS, motion clarity and where each wins
OLED panels in 2026 (LG WOLED, Samsung QD-OLED) measure 0.03 to 0.1 ms in gray-to-gray transitions because each pixel is its own emitter. The motion clarity advantage over fast IPS is real and visible during fast pans and high-speed motion. Trailing behind moving objects is essentially gone.
The catch is that response time is only one part of input lag. Some OLED gaming monitors have signal processors no faster than competing IPS panels; the total click-to-pixel latency is close. A 240Hz OLED with 5 ms of processing delay has a similar total monitor-side lag as a 360Hz fast IPS with 2 ms of processing delay, even though the OLED transitions pixels 50 times faster.
For pure motion clarity (text legibility while panning, target tracking, no smearing trail), OLED wins. For lowest total monitor-side lag, the answer depends on the specific model, not the panel technology.
Overdrive, the speed-vs-overshoot trade
LCD overdrive applies extra voltage to push pixels through their transitions faster. The downside is overshoot: the pixel briefly passes its target color and produces a faint trailing artifact behind moving objects. Most monitors have three to four overdrive levels.
The middle setting (usually labeled Normal or Standard) produces the best balance for almost all users. Off produces visible smearing; Extreme produces overshoot artifacts that are more distracting than the smearing they fix. The fastest-rated overdrive setting is rarely the best-looking one.
What number to chase for your use case
A practical guide:
- Story-driven gaming, console: 120 to 165Hz with under 15 ms total monitor lag, GtG under 5 ms is plenty
- Mixed AAA and competitive: 240Hz with under 8 ms processing delay, GtG under 3 ms
- Competitive priority: 240 to 360Hz with under 5 ms processing delay, GtG under 2 ms
- Pro esports: 360 to 540Hz with under 3 ms processing delay, fast TN or fast IPS
For our broader testing protocols and how we evaluate monitors, see our /methodology page. Related context lives in our refresh-rate explainer.
The number on the box is half the story. Measured input lag from independent reviewers is the rest. Buy a monitor whose total response-plus-lag matches your use case, not whose marketing has the smaller advertised millisecond.
Frequently asked questions
Is response time the same as input lag?+
No, and the difference matters. Response time measures how fast a single pixel changes color (typically gray-to-gray, written GtG). Input lag measures how long it takes a signal from your mouse click to appear on screen. The two specs add together for total click-to-pixel latency, but a 1 ms GtG monitor with a 25 ms processing delay will feel slower than a 4 ms GtG monitor with 8 ms of processing delay. Manufacturers advertise the smaller of the two numbers and stay quiet about the other one.
What is a good input lag number for competitive gaming?+
Total system input lag below 30 ms is excellent, 30 to 50 ms is good, 50 to 80 ms is acceptable, and above 80 ms is noticeably laggy. The monitor's contribution to that total should be under 10 ms of processing delay on a competitive panel. A 240Hz monitor with 4 ms of processing delay plus 4 ms response time plus a 4.2 ms frame time gives a panel-side total of around 12 ms, before mouse, GPU, and game-engine latency stack on top.
Does turning on overdrive reduce response time?+
Yes, but with side effects. Overdrive boosts the voltage applied to LCD pixels during transitions, which speeds up the color change. The trade-off is overshoot, where the pixel briefly passes its target color and produces a faint trail behind moving objects (inverse ghosting). Most monitors have multiple overdrive levels (Off, Normal, Fast, Extreme); the middle setting usually produces the best balance for most users. Extreme overdrive is rarely worth the overshoot artifacts even in competitive play.
Do OLED monitors really have 0.03 ms response time?+
By the measurement that manufacturers use, yes. OLED pixels change state in well under 1 ms because each pixel is a tiny LED that switches independently rather than a liquid crystal twisting in front of a backlight. The practical motion clarity advantage over fast IPS is real and visible. However, total input lag still depends on the monitor's signal processor, which on some OLED gaming monitors is no faster than a competing fast-IPS panel. The 0.03 ms figure is the pixel transition, not the full chain.
Why does my new high-end monitor feel laggy compared to my old one?+
Three common causes: a slow built-in image processor, scaler delay when running at non-native resolution, and post-processing features (dynamic contrast, AI enhancement, motion smoothing) adding milliseconds. Turn off every image-enhancement feature in the monitor menu. Run at native resolution. Use DisplayPort instead of HDMI if both are available. If lag persists, the panel's processor is the bottleneck, and software adjustments will not fix it.
David Lin
David Lin writes for The Tested Hub.