Do these two parts belong together?
Pick a processor and a graphics card. You get one number: how much one holds the other back at your resolution, and the power supply the pair needs.
Start from a graphics card
All 50What a "bottleneck" actually means
In a game, every frame needs the CPU to prepare draw calls, physics and AI, and then the GPU to render pixels. Whichever finishes last sets your frame rate. If the GPU is waiting on the CPU, you are CPU-limited; if the CPU is idling while the GPU grinds through pixels, you are GPU-limited. Being mildly GPU-limited is the normal, healthy state for a gaming PC: it means you are getting everything you paid for out of the graphics card.
Resolution shifts the balance. At 1080p the GPU has little work per frame, so a fast CPU matters most; at 4K the GPU does four times the pixel work of 1080p and even a mid-range CPU can keep up. That is why the same pair can read "CPU bottleneck" at 1080p and "balanced" at 4K.
How to read the percentage
The percentage is how far the limiting part's performance index falls short of what this pairing needs at that resolution — a model estimate from published performance indexes, not a measured FPS loss or utilisation figure. CPU-limited: under 10% balanced, 10–25% mild and rarely worth spending money on, 25–40% where an upgrade of the CPU gives visible gains, above 40% clearly mismatched. GPU-limited (the normal state for a gaming PC): up to 20% balanced, 20–40% GPU-bound, above 40% the CPU is overkill for the card.