# How much bandwidth do I need?

Works out a website’s monthly data transfer (bandwidth) from its daily visitors, pages per visit and page size, and the average connection speed in Mbps that carries it.

- Page: https://www.acalculator.org/logic/bandwidth-calculator
- JSON spec: https://www.acalculator.org/logic/bandwidth-calculator.json
- Version: 4e053f965572

## Default answer

Example with the default inputs (Visitors a day 1,000, Pages per visit 3, Average page size 2 MB, Days in the month 30, Margin factor 1): 1,000 visitors a day at 3 pages of 2 MB need 180 GB a month, an average of 0.556 Mbps.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| v | Visitors a day | The average number of visits to the site in a day. |
| p | Pages per visit | The average number of pages each visitor opens. |
| s | Average page size | The data one page view sends: the page with its images, scripts and styles. |
| d | Days in the month | How many days to count as a month. |
| f | Margin factor | A multiplier for room above the average: 1 means none; 1.5 plans for half as much again (peaks, bots, downloads). |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| monthly | Data transfer per month (GB) | Visitors × pages × page size × days × margin factor, in gigabytes (10⁹ bytes). |
| daily | Data transfer per day (GB) | The monthly figure ÷ the days. |
| mbps | Average speed (Mbps) | The monthly bits ÷ the seconds in those days, in megabits per second: the steady rate that carries it. |
| views | Page views per month | Visitors × pages × days (no margin). |

## Method

Monthly bytes = visitors a day × pages per visit × page size × days × margin factor. GB = bytes ÷ 10⁹. Average Mbps = bytes × 8 ÷ (days × 86,400 s) ÷ 10⁶.

## Assumptions

- Every page view sends the full page size; browser caching, which lowers repeat views, is not counted.
- Traffic is spread evenly over the day; the average speed is not the peak a server must handle.
- GB means 10⁹ bytes and Mbps 10⁶ bits per second; 1 byte is 8 bits.

## Worked examples

1. v = 1,000, p = 3, s = 2,000,000, d = 30, f = 1 gives monthly = 180, daily = 6, mbps = 0.555556, views = 90,000. Source: NIST, Metric (SI) prefixes (kilo 10³, mega 10⁶, giga 10⁹, tera 10¹²), https://www.nist.gov/pml/owm/metric-si-prefixes (retrieved 2026-10-05).
2. v = 25,000, p = 4.2, s = 1,500,000, d = 31, f = 1.5 gives monthly = 7,323.75, mbps = 21.875. Source: NIST, Metric (SI) prefixes (kilo 10³, mega 10⁶, giga 10⁹, tera 10¹²), https://www.nist.gov/pml/owm/metric-si-prefixes (retrieved 2026-10-05).
3. v = 500, p = 2, s = 819,200, d = 30, f = 1 gives monthly = 24.576. Source: 500 × 2 × 30 × 819,200 = 24.576 × 10⁹ bytes (NIST binary prefixes, https://physics.nist.gov/cuu/Units/binary.html, retrieved 2026-10-05).

## FAQ

### How do I calculate website bandwidth?

Multiply visitors a day by pages per visit by the average page size, then by the days in the month. 1,000 visitors a day viewing 3 pages of 2 MB each send 6 GB a day, or 180 GB in a 30-day month. Multiply by a margin factor, such as 1.5, to leave room for peaks.

### How do I find my average page size?

Open the page in a browser, open the developer tools, and look at the Network tab: it shows the total data transferred for the page. Use an average over your most visited pages, with images, scripts and styles included.

### What is the difference between bandwidth and data transfer?

Hosting plans often say "bandwidth" for the total data sent in a month, in GB or TB. Strictly, bandwidth is a rate, in Mbps. The calculator shows both: the monthly total and the average rate that would carry it.

### Why does the margin factor matter?

Traffic is not even. Busy hours, a post that goes viral, search engine bots and file downloads all add to the average. A factor above 1 plans for this; with 1.5 the page shows half as much again as the plain average.

### Is the average Mbps the speed my server needs?

No, it is the floor. It spreads the month’s data evenly over every second, but most traffic comes in a few busy hours. The peak speed a server must handle is several times the average.

### Does caching lower the bandwidth?

Yes. Browsers keep images, scripts and styles, so a visitor’s second and later pages send less. A content delivery network also serves files from its own servers. The calculator counts every page at full size, so its answer is an upper estimate.

## Sources

- NIST, Metric (SI) prefixes: kilo 10³, mega 10⁶, giga 10⁹. https://www.nist.gov/pml/owm/metric-si-prefixes (retrieved 2026-10-05)
- NIST, Prefixes for binary multiples: kibi 2¹⁰, mebi 2²⁰. https://physics.nist.gov/cuu/Units/binary.html (retrieved 2026-10-05)