Model quantization compresses neural network weights from high-precision formats like 16-bit floating point into low-precision formats such as 8-bit or 4-bit integers, cutting a model's memory footprint to roughly a quarter of its original size and letting models that once needed data-center hardware run on ordinary computers instead.
What Is Model Quantization?
Quantization compresses a neural network's weights from a high-precision format, such as 16-bit floating point, into a low-precision format such as 8-bit or 4-bit integersCITE:E1. The technique lowers both the memory a model occupies and the amount of computation needed to run itCITE:E1.
Why Does Quantization Let Large Models Fit on a Computer?
Memory usage scales roughly with the number of bits used per parameter, so reducing bit-width directly reduces file sizeCITE:E2. At FP16 precision, each parameter takes up 2 bytes; after 4-bit quantization, each parameter takes up about 0.5 bytes — roughly a quarter of the original sizeCITE:E2. That reduction is what turns a model too large to load into one that runs on hardware that previously could not hold itCITE:E2.
What Do Real Quantized Models Look Like on Disk?
Quantized file size directly determines which devices a model can run on, according to EffectStory's Mac local-LLM dataCITE:E3. Qwen3 235B, quantized with Q4, comes to about 142GB, while Phi-4 14B comes to about 8.9GB after quantizationCITE:E3. Quantization is described in that data as a precondition for running large models locallyCITE:E3.
| Item | Precision | Size |
|---|
| Generic weight | FP16 | 2 bytes/parameter |
| Generic weight | 4-bit | ~0.5 bytes/parameter |
| Qwen3 235B | Q4 quantized | ~142GB |
| Phi-4 14B | Quantized | ~8.9GB |
What Does Quantization Cost in Accuracy — and How Is That Addressed?
Quantization introduces precision loss, but modern 4-bit methods such as Q4_K_M limit that loss through grouped weights and calibrationCITE:E4. This is why 4-bit quantization has become a primary choice for local deployment: it trades a small amount of quality for several-fold gains in memory and speedCITE:E4.
How Does Quantization Work Together With Mixture-of-Experts (MoE)?
Quantization and MoE architectures reinforce each other, according to EffectStory's frontier-LLM comparison dataCITE:E5. MoE activates only part of a model's parameters at a time to cut computation, while quantization compresses the memory footprint on top of that; combined, the two make it possible for large open-source models to run on consumer-grade hardwareCITE:E5.
Where Does Quantization Hit Its Limits?
Quantization cannot make every model fit: models at the 1-trillion-parameter scale can still exceed a single machine's memory capacity even after 4-bit quantizationCITE:E6. Quantization shrinks a model's file size, but it does not change how large the model fundamentally isCITE:E6.
What Does This Mean?
The same arithmetic — FP16's 2 bytes per parameter dropping to roughly 0.5 bytes at 4-bit, about a quarter the original size — explains why Qwen3 235B lands at roughly 142GB while the much smaller Phi-4 14B lands at roughly 8.9GB: quantization scales file size down proportionally, it does not erase parameter countCITE:E2CITE:E3. Pairing quantization with MoE extends how far that scaling can go by cutting active computation as well as memoryCITE:E5, but the 1-trillion-parameter tier shows where the technique stops working: even at 4-bit, total parameter count there still outruns a single machine's memoryCITE:E6.