FitLLM

RTX 5090 vs RTX 5080 for local LLMs

RTX 5090: 13/18 models · RTX 5080: 4/18 (at ~4-bit, 8K)

Computed with the open FitLLM engine — accurate per-layer KV-cache modeling, not a naive estimate. Updated 2026-09-06.

FitLLM compares fit — what loads in memory — computed from official config.json. These are a floor, not a guarantee; speed and power are not estimated.

The two cards

RTX 5090RTX 5080
VRAM32 GB16 GB
Memory bandwidth (speed, not estimated)1792 GB/s960 GB/s

What each runs (~4-bit, max context that fits)

ModelRTX 5090RTX 5080
Qwen 3.8 27Bup to 105K · 20.7/32 GBwon't fit · 20.7/16 GB
Qwen 3.8 2.4T-A95Bwon't fit · 1565/32 GBwon't fit · 1565/16 GB
Laguna XS 2.1up to 95K · 24.0/32 GBwon't fit · 24.0/16 GB
Laguna S 2.1won't fit · 77.8/32 GBwon't fit · 77.8/16 GB
Hy3won't fit · 196/32 GBwon't fit · 196/16 GB
GLM-5.2won't fit · 484/32 GBwon't fit · 484/16 GB
GLM-4.7-Flashup to 96K · 22.6/32 GBwon't fit · 22.6/16 GB
gpt-oss-20bup to 131K · 15.8/32 GB⚠️ won't fit · 15.8/16 GB
gpt-oss-120bwon't fit · 77.1/32 GBwon't fit · 77.1/16 GB
Qwen 3.6 35B-A3Bup to 116K · 24.8/32 GBwon't fit · 24.8/16 GB
Qwen 3.6 27Bup to 109K · 20.3/32 GBwon't fit · 20.3/16 GB
Qwen-AgentWorld-35B-A3Bup to 119K · 24.6/32 GBwon't fit · 24.6/16 GB
Gemma 4 31bup to 67K · 23.5/32 GBwon't fit · 23.5/16 GB
Gemma 4 26b A4Bup to 229K · 18.9/32 GBwon't fit · 18.9/16 GB
Gemma 4 12bup to 262K · 10.4/32 GBup to 110K · 10.4/16 GB
Llama-3.1-8B-Instructup to 131K · 8.5/32 GBup to 48K · 8.5/16 GB
Llama-3.2-3B-Instructup to 131K · 5.3/32 GBup to 73K · 5.3/16 GB
MiniCPM5-1Bup to 131K · 3.2/32 GBup to 131K · 3.2/16 GB

Only the RTX 5090 runs: Qwen 3.8 27B, Laguna XS 2.1, GLM-4.7-Flash, gpt-oss-20b, Qwen 3.6 35B-A3B, Qwen 3.6 27B, Qwen-AgentWorld-35B-A3B, Gemma 4 31b, Gemma 4 26b A4B.

Bottom line

For local LLMs, more VRAM means more models and longer context. Match the card to the model you actually want to run — see the per-model fit pages.

All numbers are computed by the open-source fitllm-engine (MIT) from official model config.json values — reproduce or audit them yourself. Estimates; real usage varies with runtime (llama.cpp / MLX / Ollama), driver and display. Found a mismatch? Report it. · FitLLM home