Performance comparison: which is faster?
Core i7-8700K (Intel, 2018) and Core i5-8400 (Intel, 2018) are compared here. Compare not only scores, but also whether the motherboard can be reused and which GPU class is balanced with each CPU.
Overall performance: i7-8700K is about 55% faster
Both use the same LGA1151 socket, so they can be installed on the same motherboard. For games, performance balance with the GPU (guideline CPU:GPU = 0.9:1) matters more than CPU speed alone.
Relative performance score (higher is faster). Actual speed varies by workload, cooling, and memory configuration.
| Item | i7-8700K | i5-8400 |
|---|---|---|
| Performance Score | 15,500 | 10,000 |
| Generation | 8th Gen | 8th Gen |
| Socket | LGA1151 | LGA1151 |
| Release Year | 2018 | 2018 |
| Type | Desktop | Desktop |
| Compatible GPU Example | GeForce RTX 4060 | Radeon RX 6650 XT |
| If You Want To... | Recommended |
|---|---|
| Prioritize maximum speed for heavy work or a high-end GPU | i7-8700K |
| Upgrade while reusing the current motherboard | Either works (same LGA1151 socket) |
| Prioritize value and adequate performance | i5-8400 (the lower model is often sufficient) |
i7-8700K is about 55% higher by score (i7-8700K: 15500 points / i5-8400: 10000 points). For gaming, the GPU tier usually matters more than a few percent of CPU difference. For CPU-heavy work such as video editing and streaming, choose the faster CPU.
Both are 8th Gen-generation CPUs.Both use the same LGA1151 socket, so they can be installed on the same motherboard.
Using our CPU:GPU = 0.9:1 guideline, GeForce RTX 4060 pairs well with i7-8700K and Radeon RX 6650 XT pairs well with i5-8400. If either GPU is too strong or too weak, one part holds the other back.
