What Is Response Time (GtG)? Monitor Motion Clarity Explained

Response time (GtG, or gray-to-gray) measures how fast a pixel can transition from one color to another — typically from one shade of gray to another and back. It's measured in milliseconds (ms), with lower being better. A 1ms response time means pixels transition in 1 millisecond; a 5ms response time means pixels take 5 milliseconds. The difference determines whether fast motion in games looks clean or smeared with ghosting artifacts.

Response time is the most misunderstood monitor spec. Manufacturers advertise "1ms response" prominently, but these numbers are often misleading — measured under ideal conditions with aggressive overdrive that causes inverse ghosting. Real-world response time is typically 2–4x slower than the advertised number. Understanding what response time actually measures helps you cut through the marketing and choose a monitor with real motion clarity.

This guide explains what GtG response time is, how it affects motion clarity, why manufacturer claims are misleading, and how to test real-world response time. By the end, you'll understand this critical spec and know how to evaluate monitors based on actual motion performance rather than marketing numbers.

Manufacturer response time claims are measured under ideal conditions that don't reflect real-world use. The most common trick: measuring only the fastest transition (e.g., black-to-white-to-black) rather than the full range of gray-to-gray transitions. A monitor might achieve 1ms on one specific transition but take 5ms on others. The advertised number is the best case, not the average.

Another trick: aggressive overdrive. Manufacturers crank up the overdrive voltage to force faster pixel transitions, hitting the advertised 1ms number. But aggressive overdrive causes inverse ghosting — bright trails behind moving objects that are often worse than the original ghosting. The "1ms" setting on many monitors is unusable due to inverse ghosting; users have to use the "Normal" or "Fast" setting, which delivers 3–5ms real-world response.

The only reliable way to evaluate response time is reading independent reviews that measure real-world GtG across multiple transitions. RTings and TFTCentral use standardized testing that measures average and worst-case response times across the full gray-to-gray range. Their numbers are typically 2–4x slower than manufacturer claims but reflect what you'll actually see. For more on motion testing, see our ghosting test and the refresh rate test.

Response time and refresh rate are often confused but measure different things. Refresh rate is how many frames per second the display shows (144Hz = 144 frames/second). Response time is how fast each pixel can change color (1ms = 0.001 seconds per transition). Both affect motion clarity, but they interact in specific ways.

If response time is slower than frame time, pixels can't fully transition before the next frame arrives, causing persistent ghosting. At 144Hz (6.9ms frame time), you need response time under 6.9ms for clean motion. At 240Hz (4.2ms frame time), you need under 4.2ms. This is why high refresh rate monitors require fast response time — a 240Hz monitor with 8ms response produces worse motion than a 144Hz monitor with 2ms response.

For most gamers, response time matters more than refresh rate above 144Hz. The jump from 60Hz to 144Hz is transformative (smooth motion). The jump from 144Hz to 240Hz is subtle (marginally smoother). But the jump from 5ms to 1ms response is visible in every fast-paced game (cleaner motion, less ghosting). When choosing a gaming monitor, prioritize response time over refresh rate above 144Hz. For more, see our 240Hz vs 144Hz guide and the panel type guide.