How to Use the FPS Input Lag Calculator
Enter your in-game FPS, monitor refresh rate (Hz), and panel type to estimate total input lag — the time from pressing a key or moving a mouse to seeing the result on screen. This calculation covers rendering and display latency only (no network ping).
Formula: Total input lag ≈ frame time (1000/FPS) + average scanout delay (1000/Hz ÷ 2) + panel response time. Example: 144 FPS on a 144 Hz IPS monitor gives 6.94 + 3.47 + 4 = ~14.4 ms. Upgrading to 240 Hz cuts scanout delay to 2.08 ms, saving roughly 3 ms.
This estimate assumes V-Sync off, no GPU render queue buffering, and excludes USB input latency and system processing delays. Real-world input lag is typically slightly higher. For online games, add your network ping for the full end-to-end figure.
Frequently Asked Questions
Higher FPS reduces frame time (1000/FPS), cutting rendering latency. You need both high FPS and a high-Hz monitor to see the full benefit.
Yes, with V-Sync off. Extra FPS reduces rendering latency even if the display can't show all frames, so the frame the monitor does show is more current.
No. This tool covers local rendering and display latency only. For online games, add your ping to get the full end-to-end input lag estimate.