A100 40GB vs A100 80GB
The A100 80GB holds 46 models from our catalog that the A100 40GB cannot fit at Q4_K_M, and decodes about 1.3× faster on memory bandwidth. Decode speed on a memory-bound workload scales with bandwidth, so that ratio is the number that matters once the model fits at all.
Specs side by side
| Spec | A100 40GB | A100 80GB |
|---|---|---|
| VRAM | 40 GB | 80 GB |
| Memory bandwidth | 1555 GB/s | 2039 GB/s |
| TDP | 400 W | 400 W |
| Models that fit (Q4_K_M) | 427 of 506 | 473 of 506 |
Form factor: A100 40GB figures are for the SXM4 module, A100 80GB figures are for the SXM4 module. PCIe/NVL variants differ in bandwidth and TDP — see the A100 40GB page and methodology.
What the extra VRAM actually buys
46 models in our catalog fit on the A100 80GB at Q4_K_M but not on the A100 40GB. The largest of them:
Pixtral Large 124B InstructMistral Large 123B (2407) InstructMistral Large 123B (2411) InstructGPT-OSS 120B (5.1B active) InstructCommand A 111B ChatQwen 1.5 110B
Largest model each can run
At Q4_K_M the biggest fit in our catalog is Qwen 2 57B-A14B Instruct (34.5 GB) on the A100 40GB, and Pixtral Large 124B Instruct (74.3 GB) on the A100 80GB. Both figures are weights plus runtime overhead; KV cache for your context is extra.
Power and running cost
At 8 hours a day the A100 40GB draws about 96 kWh a month against 96 kWh for the A100 80GB — a difference of 0 kWh. Multiply by your own tariff; we do not assume one. Board TDP is the rated figure, not measured draw.
FAQ
A100 40GB vs A100 80GB: which should I buy for local AI?
The A100 80GB fits 473 of the 506 models in our catalog at Q4_K_M against 427 for the A100 40GB, and has about 1.3× the memory bandwidth, which is what sets decode speed once a model fits. If the models you run already fit the A100 40GB, the extra spend buys context length and speed, not a new model tier.
Is the A100 80GB faster than the A100 40GB?
On memory-bound decoding, yes — roughly 1.3× the throughput, since token generation scales with memory bandwidth (2039 GB/s vs 1555 GB/s). This is an upper bound from bandwidth alone, not a measured benchmark.
How much more VRAM does the A100 80GB have?
40 GB more (80 GB vs 40 GB). That difference lets it hold 46 additional models from our catalog at Q4_K_M.
Need a third card in the mix? The interactive compare tool lines up any three. To size KV cache for your context length, use the GPU Memory Calculator.
Related matchups
Other head-to-heads involving these cards:
A100 40GB vs L40SA100 80GB vs H100 80GBRTX 5090 vs A100 40GBA100 40GB vs RTX A6000RTX A6000 vs A100 80GB
New to sizing? What VRAM is and why bandwidth sets decode speed cover the basics, and quantization explains the formats in the table above. Common mistakes when sizing VRAM lists the traps.