Bandwidth Calculator — how much transfer your traffic really uses
Estimate monthly data transfer from visits, pages per visit and page weight, with headroom and growth projection.
Free and instant — results appear in seconds. No sign-up, no limits, and nothing you type is stored.
Hosting plans quote bandwidth in figures most people cannot map onto their actual traffic. This converts visits, pages per visit and average page weight into monthly transfer, then adds headroom for the uneven days.
The input that matters most and is guessed most often is page weight. Open your browser's network tab, hard-reload a typical page, and read the transferred total. It is usually larger than expected — the median page has been growing for years, and image-heavy pages routinely exceed 3 MB.
Working through a real site
A small business site: 25,000 monthly visits, 3 pages per visit, 2.4 MB average page.
Monthly transfer 175.78 GB
With 30% headroom 228.52 GB
Daily average 5.86 GB
Peak day (3× average) 17.58 GB
In 12 months at 5% growth 315.72 GBThree things worth drawing out.
The 30% headroom is not padding. Traffic is not evenly distributed. A newsletter send, a post that gets shared, or a seasonal peak produces days several times the average. Sizing to the mean means overage charges on the days that matter most.
The peak day figure is the one to check against any daily cap. Some hosts enforce daily as well as monthly limits, and a launch day hitting three times average is normal rather than exceptional.
The growth projection compounds. Five percent a month is a modest-sounding figure that produces a 1.8× increase over a year. Sizing to today's traffic on an annual contract means outgrowing the plan around month eight.
What this does not count: file downloads, video, email traffic on the same account, and backups if they run over the same allowance. Any of those can dwarf page delivery. A single 50 MB PDF downloaded a thousand times is 50 GB — more than a quarter of this site's entire page traffic.
Page weight is where the estimate lives or dies
Everything else here is arithmetic. If page weight is wrong, the result is wrong proportionally.
Measure it rather than guessing: open DevTools, switch to Network, hard-reload, and read the transferred figure at the bottom. Do this on your heaviest realistic page, not the lightest.
Note the difference between transferred and resources. Transferred is what crossed the wire after compression, and that is the number bandwidth is billed on.
What a CDN changes
A CDN serves static assets — images, CSS, JavaScript, fonts — from its own network. Those bytes never touch your origin server.
On a typical site that is 60–80% of total weight, so origin bandwidth drops correspondingly. If your host bills for transfer and your CDN has a generous free tier, this is the cheapest bandwidth reduction available.
It does not reduce total bytes delivered. It moves who pays for them.
Reducing the underlying number
Before buying more allowance:
Serve WebP or AVIF. Typically 25–50% smaller than JPEG at equivalent quality.
Size images to their display dimensions. Serving a 4000px photo into a 800px slot wastes most of the bytes downloaded.
Enable compression. GZIP or Brotli on HTML, CSS and JavaScript cuts those files by 60–80%. Free, and frequently not switched on.
Set cache headers. Returning visitors should not re-download unchanged assets.
Lazy-load below-the-fold images. Bytes for images nobody scrolls to are pure waste.
These routinely halve page weight, which halves the bandwidth requirement.
"Unlimited" bandwidth
Unlimited plans are governed by an acceptable use policy rather than a stated cap, and the policy always contains a resource-abuse clause. The practical limit exists; it is simply undisclosed and enforced at the provider's discretion.
For a normal website this is fine and you will never approach it. For file hosting, video, or anything that transfers heavily, expect to be moved to a metered plan — and read the AUP before committing.
Bandwidth is rarely the real constraint
Most sites that outgrow shared hosting do so on CPU, memory or database concurrency, not transfer. A plan with generous bandwidth and tight process limits will fail under a traffic spike long before the transfer allowance is touched.
Use this figure to check you are not undersized, then look at the resource limits that actually bind.
Frequently asked questions
How do I find my average page size?
Open your browser's developer tools, switch to the Network tab, and hard-reload a typical page. The transferred total at the bottom is the figure to use — it reflects what actually crossed the wire after compression. Measure a representative page rather than your lightest one.
Does a CDN reduce my bandwidth usage?
It reduces bandwidth billed to your origin server, typically by 60 to 80 percent, because static assets are served from the CDN's network instead. The total bytes delivered to visitors are unchanged — the CDN simply pays for most of them.
What does unlimited bandwidth actually mean?
It means there is no stated cap, but the acceptable use policy contains a resource-abuse clause that functions as one. For a normal website you will never approach it. For file hosting or video, expect to be moved to a metered plan, and read the policy before committing.
Why add 30% headroom?
Traffic is not evenly distributed across the month. A newsletter send, a shared post or a seasonal peak can produce days several times the average. Sizing to the mean means hitting overage charges precisely on the days that matter most.
Does this include email and backups?
No. It estimates web page delivery only. File downloads, video streaming, email traffic and backups running over the same allowance are all additional, and any of them can exceed page traffic substantially. A single 50 MB file downloaded a thousand times is 50 GB.
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