Quantization and choosing a quant
A quant is a smaller copy of a model; Q4_K_M is the default balance of size and quality, and higher numbers such as Q8_0 are closer to the original but need more memory.
A model is billions of numbers. Quantization stores each number with fewer bits, so the file is smaller, loads faster and fits a cheaper GPU. The trade is a small loss in quality.
Common quants
| Quant | Bits per number (about) | Size of an 8B model | Quality |
|---|---|---|---|
Q4_K_M | 4.5 | about 5 GB | Good. The default. |
Q5_K_M | 5.5 | about 6 GB | Better |
Q6_K | 6.5 | about 7 GB | Very close to the original |
Q8_0 | 8.5 | about 9 GB | Near full quality |
F16 / BF16 | 16 | about 16 GB | Full quality, the original |
FP8 (safetensors) | 8 | about 9 GB | Near full quality on vLLM |
A quick estimate: size in GB is about the number of parameters (in billions) times the bits, divided by 8.
How to choose
- Start with the default
Q4_K_Mon an L4. For most chat and support use it is hard to tell apart from the original. - If answers feel careless with facts, numbers or code, try
Q6_KorQ8_0. - If a bigger model in
Q4_K_Mfits the same GPU as a smaller model inQ8_0, the bigger model usually wins. - For the best throughput with many users at once, use a safetensors or FP8 repo on vLLM.
Pick a quant
Add it after the repo:
bitsrun deploy hf:unsloth/Qwen3-8B-GGUF:Q8_0Or paste the link to one .gguf file from the repo's file list. Ollama names choose their quant by tag, for example qwen3:8b-q8_0 where the library lists it.
Switch later
You do not have to redeploy. Open Performance on the endpoint card and choose Fastest, Balanced or Best quality. Each shows its quality badge (Full, Near full, Reduced or Low quality), speed, GPU and price before you switch. See Performance.
What can go wrong
| Message | What to do |
|---|---|
| "This repo has no file with that quantization." | Leave it empty to use Q4_K_M, or name one the repo lists. |
| "This repo only has GGUF files split into parts" | Split files are not supported yet. Pick a repo with single-file quants. |
| "This repo keeps its model files in folders." | Open the .gguf file you want on Hugging Face and paste its link. |
Still stuck?
Email support@bitsrun.com with what you tried and any request id you saw. A real person answers.