What is website bandwidth?
Bandwidth, or data transfer, is the amount of data your server sends to visitors: every page, image, script and video they load. Hosting plans either set a monthly limit in gigabytes or call it “unmetered”, which usually means a fair-use limit. Knowing your real need stops you overpaying, and stops your site being slowed or suspended in a busy month.
Formulas
Bandwidth = visitors × pages per visit × page size × (1 + headroom ÷ 100)Speed in Mbps = data in megabits ÷ seconds
Worked example
20,000 visitors a month who each view 3 pages of about 2 MB use 175.8 GB a month with 50% headroom — 5.8 GB a day.
How to use the website bandwidth calculator
- Enter your figures: visitors per month, pages per visit and average page size. Extra headroom is optional and counts as zero when left empty.
- Read the result. It updates as you type, so there is no button to press.
- Try other numbers to compare scenarios. Reset brings back the example values.
Getting it right
- Find your average page size in your browser’s developer tools (Network tab) or a speed-test tool; most pages are 1–3 MB.
- Images are usually most of the weight. Compressing them and serving WebP can halve your bandwidth.
- A CDN such as Cloudflare serves cached files for you, so much of the bandwidth never reaches your host.
Frequently asked questions
How much bandwidth do I need for 10,000 visitors?
With 3 pages per visit at 2 MB each, about 59 GB a month, or around 88 GB with 50% headroom.
Is bandwidth the same as speed?
Not quite. Hosting plans use “bandwidth” for the total data sent per month. Speed is how fast data moves at a given moment, measured in megabits per second.
What does unmetered bandwidth mean?
There is no fixed monthly limit, but there is usually a fair-use policy and a cap on speed. It is fine for most small and medium sites.