Microsoft, United States · Released December 11, 2024
phi-4 has 14.7B parameters. In BF16 its weights alone take 27.3 GiB; quantized to 4-bit, about 8.35 GiB. Cheapest way to run it today: 1 × RTX A4000 (16 GB) at $0.092 per hour.
Read every day from Hugging Face. Split files are added together; vision projectors are left out.
How many GPUs to run phi-4
Fewest GPUs that fit the weights plus one 8K-token request. Data-center GPUs use vLLM (90% of memory usable), the others llama.cpp. Several GPUs split the model with tensor or pipeline parallelism.
GPU
BF16 / FP16
8-bit
4-bit
GeForce RTX 4090 24 GB
2
1
1
GeForce RTX 5090 32 GB
1
1
1
RTX PRO 6000 Blackwell 96 GB
1
1
1
Mac M5 Max 128 GB 96 GB usable
1
1
1
NVIDIA H100 80 GB
1
1
1
NVIDIA H200 141 GB
1
1
1
NVIDIA B200 (HGX) 180 GB
1
1
1
8-bit: FP8 with vLLM (INT8 on GPUs without FP8), Q8_0 with llama.cpp. 4-bit: AWQ / GPTQ with vLLM, Q4_K_M with llama.cpp, both counted at the Q4_K_M size.
Cheapest way to run phi-4 today
For each GPU: the fewest cards that fit phi-4 with one 8K-token request, the most faithful weight format at that count, and the cheapest on-demand price (2026-10-14).
On-demand prices from RunPod, Vast.ai, Azure, Oracle Cloud, OVHcloud, Scaleway, Verda and Akash, checked every hour. Serving many users needs more KV cache, so more memory: size it in the calculator. Some links are affiliate links: StudioTV may earn a commission, at no extra cost to you.
KV cache: how memory grows with context
Architecture: 40 layers · 40 full attention (10 KV × 128). Every layer keeps keys and values for every token (grouped-query attention), so the cache grows linearly with context.
Context per request
BF16 cache
FP8 cache
8K tokens
1.56 GiB
0.78 GiB
phi-4 VRAM FAQ
How much VRAM does phi-4 need?
In BF16 the weights alone take 27.3 GiB (29 GB). In FP8 that is 14.6 GiB, and about 8.35 GiB with 4-bit quantization (Q4_K_M). Each request then adds KV cache: 1.56 GiB at 8K tokens (BF16 cache).
Can phi-4 run on a single RTX 4090 (24 GB)?
Yes. In Q8_0 it fits on one RTX 4090 with an 8K-token context (16.2 GiB including the cache, with llama.cpp).
What is the cheapest way to run phi-4?
On 2026-10-14, the cheapest on-demand setup is 1 × RTX A4000 (16 GB) with Q4_K_M weights on Vast.ai, at $0.092 per hour (about $67.16 per month). Next: 1 × GeForce RTX 3090 (24 GB) with Q8_0 weights on Vast.ai, at $0.149 per hour. Sized for one 8K-token request; prices are checked every hour.
How many H100 GPUs does phi-4 need?
With one request and an 8K-token context: 1 in BF16, 1 in FP8 and 1 in 4-bit (vLLM, 90% of memory usable). Serving many users at once needs more memory for their KV caches: the calculator sizes that for you.
phi-4 VRAM badge
For a model card or a README: the 4-bit size and the smallest GPU it fits on, linked to this page. Data as JSON: /api/models/phi-4.json.
Estimates, not guarantees: computed from the official config.json with the same engine as the LLM VRAM Calculator. Real usage depends on your engine version and settings.