How much VRAM does Phi-3.5 mini (3.8B) need?
Phi-3.5 mini (3.8B) needs about 10.2 GB of GPU memory at FP16 and about 4.7 GB at 4-bit. Pick a precision below to see which ComputeBD AI Computer fits and what it costs per hour in taka.
You need about 10.2 GB of GPU memory to run Phi-3.5 mini (3.8B) at FP16 / BF16.
- Model weights 7.1 GB
- Conversation memory (KV cache) 1.5 GB
- Runtime & working space 1.6 GB
NVIDIA L4 is the most affordable AI Computer that fits — ৳147/hour, billed by the minute.
| AI Computer | Fits? | Speed (1 user) | Price |
|---|---|---|---|
| NVIDIA L424 GB | Fits |
≈ 24 tokens/s | ৳147/hr |
| NVIDIA A1024 GB | Fits |
≈ 47 tokens/s | ৳196/hr |
| NVIDIA L40S48 GB | Fits |
≈ 68 tokens/s | ৳343/hr |
| NVIDIA A10080 GB | Fits |
≈ 160 tokens/s | ৳638/hr |
| NVIDIA H10080 GB | Fits |
≈ 263 tokens/s | ৳1,047/hr |
| NVIDIA H200141 GB | Fits |
≈ 377 tokens/s | ৳1,390/hr |
| NVIDIA B200180 GB | Fits |
≈ 628 tokens/s | ৳1,652/hr |
| NVIDIA B300288 GB | Fits |
≈ 628 tokens/s | ৳1,880/hr |
Phi-3.5 mini (3.8B) at each precision
| Precision | GPU memory needed | Cheapest ComputeBD AI Computer |
|---|---|---|
| FP32full precision — rarely needed | 17.9 GB | NVIDIA L4 · ৳147/hr |
| FP16 / BF16standard — original quality | 10.2 GB | NVIDIA L4 · ৳147/hr |
| 8-bitalmost no quality loss | 6.6 GB | NVIDIA L4 · ৳147/hr |
| 4-bit (GGUF / AWQ / GPTQ)small quality loss, ~4× less memory | 4.7 GB | NVIDIA L4 · ৳147/hr |
- Made by
- Microsoft
- Parameters
- 3.82B
- Max context
- 131,072 tokens
- LoRA / QLoRA fine-tune
- ≈ 9.8 GB / 4.6 GB
- Hugging Face
- microsoft/Phi-3.5-mini-instruct
How the estimate works
- Weights = parameters × bytes per parameter (FP16 = 2 bytes, 8-bit ≈ 1, 4-bit ≈ 0.56).
- KV cache (conversation memory) grows with context length and the number of people at once: 2 × layers × KV-heads × head size × tokens × 2 bytes.
- Runtime: about 1 GB for CUDA plus ~8 % of the weights for working space.
- Fine-tuning: LoRA keeps an FP16 copy of the model and trains ~1 % extra parameters; QLoRA keeps a 4-bit copy; full fine-tuning needs ~16 bytes per parameter. Gradient checkpointing is assumed.
- Speed: generating text for one user is limited by memory bandwidth, so tokens/second ≈ bandwidth × 60 % ÷ model size.
These are good planning estimates, not guarantees: the real figure depends on the software (vLLM, llama.cpp, Transformers…), settings and your data. Leave ~10 % spare.
VRAM needed, model by model
Frequently asked questions
How much VRAM does Phi-3.5 mini (3.8B) need?
About 10.2 GB at FP16 (original quality) and about 4.7 GB at 4-bit, for one user with a 4k context.
Which GPU can run Phi-3.5 mini (3.8B)?
At full quality it fits on an NVIDIA L4 (24 GB), ৳147/hour on ComputeBD.
How much VRAM to fine-tune Phi-3.5 mini (3.8B)?
About 9.8 GB with LoRA and 4.6 GB with QLoRA (sequence length 2,048, batch 1, gradient checkpointing). Estimate the time and cost with the fine-tuning cost estimator.
Try it on a real AI Computer
JupyterLab opens in about a minute. Pay in taka with bKash, billed by the minute — stop whenever you like.