The gap changes with resolution.
CPU differences shrink as resolution rises — at 4K the graphics card does most of the work.
| Resolution | i9-11900K | i5-12400F | Difference |
|---|---|---|---|
| 1080p | 79 | 77 | +3% |
| 1440p | 76 | 74 | +3% |
| 4K | 74 | 71 | +4% |
In a real build with a RTX 3080.
Specs alone don’t tell you which to buy. Here is what each one does when it’s actually paired up, at 1440p.
| Game (1440p, paired with the RTX 3080) | i9-11900K | i5-12400F |
|---|---|---|
| League of Legends | 303 fps | 300 fps |
| Counter-Strike 2 | 261 fps | 257 fps |
| Grand Theft Auto V | 130 fps | 129 fps |
| Elden Ring | 106 fps | 106 fps |
| Cyberpunk 2077 | 81 fps | 81 fps |
| Starfield | 81 fps | 80 fps |
Modelled from benchmark data, not measured for every pairing. Our published error rate is 21.6% mean absolute error.
So which should you buy?
Whichever is cheaper on the day. There is roughly 3% between them at 1440p, which you will not notice in a game.
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Common questions.
Straight answers on the i9-11900K versus the i5-12400F.
Is the i9-11900K better than the i5-12400F?
They are close enough to call a tie. At 1440p the i9-11900K scores 76 on our index against 74 for the i5-12400F — a gap of about 3%, which is inside the margin where you would not feel a difference while gaming. Buy whichever is cheaper or easier to find.
Does the i9-11900K or i5-12400F bottleneck a RTX 3080?
Paired with a RTX 3080 at 1440p, the i9-11900K build comes out balanced, and the i5-12400F build comes out balanced. Being GPU-bound is the healthy outcome — it means the graphics card is the part working hardest.
Is it worth upgrading from the i5-12400F to the i9-11900K?
No. A 3% index gap will not be visible in games, and the money is better spent on the other side of the build — usually the GPU.
Which is better value, the i9-11900K or the i5-12400F?
On performance per dollar at MSRP, the i5-12400F wins. The i9-11900K lists at $539 for an index of 76, and the i5-12400F at $174 for 74.
Check either one against your build.
Pick a CPU and its counterpart, and get a verdict at all three resolutions in under 30 seconds.