GPU memory bandwidth calculator
Memory bandwidth is how quickly a graphics card can move data to and from its video memory. Enter the bus width and the memory speed from a spec sheet to get the figure in gigabytes per second.
What memory bandwidth means
Every frame your graphics card draws needs textures, geometry and intermediate data to be read from and written to video memory. Bandwidth is the rate at which that traffic can flow, measured in gigabytes per second. A card with more bandwidth can feed its shaders without waiting, which matters most at high resolutions, with ray tracing and with large textures.
The figure comes from two numbers on a spec sheet. The bus width is how many bits travel in parallel, such as 128, 192 or 256. The memory speed is the data rate each pin carries, quoted in gigabits per second. Multiply them and divide by eight to convert bits to bytes. For example, a 256-bit bus running at 28 Gbps moves 896 gigabytes every second.
Bandwidth at common bus widths and speeds
These values apply the formula directly. They are examples of the arithmetic, not a list of specific graphics cards.
| Bus width | 21 Gbps | 28 Gbps | 32 Gbps |
|---|---|---|---|
| 128-bit | 336 GB/s | 448 GB/s | 512 GB/s |
| 192-bit | 504 GB/s | 672 GB/s | 768 GB/s |
| 256-bit | 672 GB/s | 896 GB/s | 1024 GB/s |
| 384-bit | 1008 GB/s | 1344 GB/s | 1536 GB/s |
Why bus width alone can mislead
It is tempting to rank cards by bandwidth, but modern designs complicate that. Many recent graphics cards use large on-chip caches that satisfy a big share of requests without touching video memory, so a narrower bus can perform better than the raw number suggests. Faster memory types raise the speed per pin and can offset a smaller bus. Compare bandwidth between cards with similar cache designs, and rely on real benchmarks for final decisions.
It also helps to think in terms of per-frame budget. At 60 frames per second, a card with 504 gigabytes per second has 8.4 gigabytes of traffic to spend on each frame. That is plenty at 1080p and tighter at 4K with heavy effects, which is one reason high resolutions favour wider buses.
Using the calculator
Pick the bus width and enter the memory speed. If you are comparing two cards, run the calculator twice and compare the results, or use the table to see the same memory speed on different bus widths. Use the frame rate box to see how much traffic is available per frame. If you are shopping, pair this with the VRAM calculator to check capacity and the GPU comparison tool for estimated performance.
Remember that bandwidth is only one part of a card. Shader count, clock speed, cache and drivers all shape the final frame rate, so treat this as a way to understand a spec sheet rather than a ranking tool.
How to use the gPU memory bandwidth calculator
- Find the memory bus width on the official spec page.
- Find the memory speed in Gbps per pin. Convert if it is listed in MHz.
- Select the width and enter the speed.
- Read the bandwidth and compare it with another card by running the tool again.
- Use the frame rate box to see the traffic available per frame.
Common mistakes to avoid
- Mixing up megahertz and gigabits per second. Check the units.
- Comparing bandwidth between very different cache designs.
- Treating bandwidth as a ranking. It is only one part of a card.
Related tools and guides
Keep going with these: VRAM calculator, GPU comparison tool, PCIe bandwidth checker, monitor PPI calculator, how much VRAM you need for gaming.
Frequently asked questions
How do you calculate GPU memory bandwidth?
Multiply the memory bus width in bits by the memory speed in gigabits per second per pin, then divide by eight. For a 256-bit bus at 28 Gbps that is 256 times 28 divided by 8, which equals 896 gigabytes per second.
Does more memory bandwidth always mean more FPS?
No. It helps when memory is the bottleneck, such as at 4K or with ray tracing, but shaders, clocks and cache also limit performance. A card with big caches can outperform one with more raw bandwidth, so compare benchmarks as well as specs.
What is the difference between VRAM size and bandwidth?
Size is how much data video memory holds, while bandwidth is how fast data moves in and out. A card can have plenty of memory but low bandwidth, or the reverse. Games need enough capacity to fit textures and enough bandwidth to feed the shaders.
Why do some cards have narrow buses?
Narrow buses lower cost and board complexity, and large caches plus faster memory can offset the reduced bandwidth. Designers trade bus width against cache and memory speed. At higher resolutions, narrower buses can fall behind because the cache hits less often.
Where do I find a card's memory speed?
Check the official specification page or a database of the card. Memory speed is listed in Gbps per pin, sometimes called the effective data rate. Some listings show it in MHz, so check the units and confirm whether the figure is the effective rate.
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