A GPU Calculator That Helps Calculate What GPU to Use
30 comments
·July 24, 2025zargon
oktoberpaard
It gives weird results for me. I’m using Qwen3-32B with 32K context length at Q4_K_M, with 8 bit KV cache fully offloaded to 24GB VRAM. According to this calculator this should be impossible by a large margin, yet it’s working for me.
Edit: this might be because I’ve got flash attention enabled in Ollama.
zeroq
This one is indeed much better and it instantly answers my immediate feedback I wanted to leave for the one originally posted, which is - instead of calculating an artificial scenario I would like to state what can I run on the hardware I actually have at hand. Thanks!
yepyip
Somehow you have to login now, to use it. It wasn't like this a few weeks ago...
mdaniel
That is not my experience, maybe your IP is flagged as hammering their site?
jwrallie
Nice! I could have saved so much time downloading models to do trial end error with this.
kouteiheika
The training memory breakdown is wildly inaccurate.
- No one trains big models in FP32 anymore.
- Gradients can also often be in BF16, and they don't actually have to be stored if you're not using gradient accumulation or if you're accumulating them directly in the optimizer's state.
- 32-bit Adam is silly; if you don't have infinite VRAM there's no reason why you wouldn't want to use 8-bit Adam (or you can go even lower with quantized Muon)
- Activations? They take up memory too, but are not mentioned.
It shows that to train a 3.77B parameter model I need 62GB of VRAM; just to give you some perspective for how overestimated this is: a few weeks back I was training (full fine-tuning, not LoRA) a 14B parameter model on 24GB of VRAM using every trick in the book to lower VRAM usage (to be fair, not all of those tricks are available in publicly available training harnesses, but the point still stands that even with an off-the-shelf training harness you can do a lot better than what this calculator suggests).
ethan_smith
Great points about training optimizations. For inference, similar dramatic memory reductions are possible through quantization (INT4/INT8) which can reduce VRAM needs by 2-8x compared to FP16, allowing much larger models on consumer GPUs.
fooker
Fine tuning and training are very different beasts.
kouteiheika
No they're not? The process is essentially exactly the same, just with a much lower total FLOPs budget, since if you're not training from scratch then you don't need to train for as long. I can use *exactly* the same code that I used to fine-tune a model to train a new model from scratch; literally the only difference is whether I initialize the initial weights randomly or with an existing model, a couple of hyperparameters (e.g. for training from scratch you want to start at a higher LR), and training for longer.
fooker
No, if you try to train an LLM like you're suggesting:
- you'll get something similar to gpt2.
- To approach the scale of modern LLMs, you'll need about 10x more than all the GPUs in the world.
It's a neat abstraction to consider these the same, but do you think Meta is paying 100M for writing a 15 line script?
funfunfunction
This is a cheap marketing ploy for a GPU reseller with billboards on highway 101 into SF.
ChadNauseam
Hate those ads. "Inference isn't just a buzzword". Who thought it was? (No comment on whether the linked post is a useful tool, I haven't played with it enough to know)
mdaniel
> 0 Model Available
Who in the world is expected to populate 11 select/text fields with their favorite model data points they just happen to have lying around, only to see an absolutely meaningless "295% Inference" outcome
What a dumpster
LorenDB
Where's AMD support? I have a 9070 XT and would love to see it listed on here.
nottorp
What GPU to use for what? Witcher 4? Death Stranding?
amanzi
I would have liked to see the RTX 5060 Ti with 16GB mentioned. I can't tell if it's omitted because it won't work, or if it's excluded for some other reason?
amatecha
Yeah, weird miss, but maybe just because it came out more recently. It can be used for ~anything a 5070 could be used for, no? Maybe slower, but still.
daft_pink
It would be really nice if you could import the standard models so we could see what kind of gpu we would need for popular models in the news and on hugging face
amelius
I selected LLama 3 70B, and then it said all the GPUs are insufficient for training :(
null
chlobunnee
I built a calculator to help researchers and engineers pick the right GPUs for training and inference workloads!
It helps compare GPU options by taking in simple parameters (# of transformer layers, token size, etc) and letting users know which GPUs are compatible + their efficiency for training vs inferencing.
The idea came from talking with ML researchers frustrated by slow cluster queues or wasting money on overkill GPUs.
I'd love feedback on what you feel is missing/confusing!
Some things I'm thinking about incorporating next are >Allowing users to directly compare 2 GPUs and their specs >Allowing users to see whether a fraction of the GPU can complete their workload
I would really appreciate your thoughts/feedback! Thanks!
timothyduong
Where's 3090? Or should that fall in the 4090 (24GB VRAM) category?
The best VRAM calculator I have found is https://apxml.com/tools/vram-calculator. It is much more thorough than this one. For example, it understands different models' attention schemes for correct KV cache size calculation, and supports quantization of both the model and the KV cache. Also, fine-tuning. It has its own limitations, such as only supporting specific models. In practice though, the generic calculators are not very useful because model architectures vary (mainly the KV cache) and end up being way off. (Not sure whether or not it would be better to discuss it separately, but I submitted it at https://news.ycombinator.com/item?id=44677409)