“Bandwidth” questions come in three shapes. How much data will this use? How fast a connection do I need to move this much data in time? And how much traffic will my website serve? This calculator answers each one, keeping bits and bytes straight — the source of most bandwidth mistakes — and showing both decimal (GB) and binary (GiB) sizes.
How to use the bandwidth calculator
- Choose what to calculate.
- Data used: enter a data rate (Kbps, Mbps, Gbps, or KB/s, MB/s, GB/s) and how long. You get the total, plus per hour, per day and per 30 days of nonstop use, and how many hours it takes to reach a 1 TB cap.
- Bandwidth needed: enter the amount of data, the time available and an allowance for protocol overhead. You get the required Mbps and a table of link speeds that would or would not fit the window.
- Website traffic: enter visits per month, pages per visit, average page weight and a peak-to-average ratio. You get monthly transfer, average throughput and the peak rate to plan for.
- Review the steps under the result to see each unit conversion.
Bandwidth formulas
Decimal prefixes are used throughout, as network and storage vendors do: 1 Mbps = 1,000,000 bits per second and 1 GB = 1,000,000,000 bytes. Operating systems often report sizes in binary units (1 GiB = 1,073,741,824 bytes), so a “6.75 GB” total appears as 6.29 GiB in some file managers.
Worked example: streaming
How much data does 3 hours of Full HD video at 5 Mbps use?
Rate: 5 Mbps = 5,000,000 bits per second. Time: 3 h = 10,800 s.
Bits: 5,000,000 × 10,800 = 54,000,000,000. Bytes: ÷ 8 = 6,750,000,000.
Data used: 6.75 GB (2.25 GB per hour). At that rate a 1 TB monthly cap allows about 444 hours.
The same 3 hours in 4K at 25 Mbps would use 33.75 GB — five times as much.
Worked example: backup window
You need to copy 200 GB to an off-site server within an 8-hour night, allowing 10% overhead.
Bits: 200 × 10⁹ × 8 = 1.6 × 10¹² bits. Seconds: 8 × 3,600 = 28,800.
Raw rate: 1.6 × 10¹² ÷ 28,800 = 55.6 Mbps. With overhead: 55.6 ÷ 0.9 = 61.7 Mbps sustained.
A 50 Mbps upload would need about 9 hours 52 minutes and miss the window; 100 Mbps finishes in under 5 hours.
Typical data rates
| Activity | Typical rate | Data per hour |
|---|---|---|
| Music streaming, high quality | 320 kbps | 144 MB |
| CD-quality audio, uncompressed | 1.411 Mbps | 635 MB |
| HD video call (720p) | about 1.5 Mbps | 675 MB |
| Standard-definition video | about 3 Mbps | 1.35 GB |
| Full HD video (1080p) | about 5 Mbps | 2.25 GB |
| 4K Ultra HD video | about 25 Mbps | 11.25 GB |
Streaming services adapt quality to your connection and use newer codecs over time, so treat these as planning figures.
Website bandwidth
With 50,000 visits a month, 3 pages per visit and 2.5 MB per page, a site serves 150,000 × 2.5 MB = 375 GB a month. Spread over 30 days that averages only 1.16 Mbps, but traffic bunches into busy hours, so plan for a peak several times higher — about 4.6 Mbps at a 4× ratio. A CDN, image compression and browser caching cut the bytes your origin server actually sends.
To estimate how long one download takes on your connection, use the download time calculator. To convert between MB, MiB, GB and other storage units, open the data storage converter, and for the size of a video at a given bitrate, the video file size calculator.
Frequently asked questions
How many GB does 1 Mbps use in an hour?
0.45 GB. One megabit per second for 3,600 seconds is 3,600 megabits, and dividing by 8 bits per byte gives 450 megabytes. Multiply by your rate: a 5 Mbps stream uses 2.25 GB per hour.
Why are internet speeds in bits but file sizes in bytes?
Networking has always measured line rate in bits per second, while storage counts bytes of 8 bits. So a 100 Mbps connection moves at most 12.5 megabytes per second, before protocol overhead.
How much bandwidth do I need to back up 1 TB overnight?
To move 1 TB in 8 hours you need 1 × 10¹² × 8 bits ÷ 28,800 s = 278 Mbps of throughput, or about 309 Mbps with 10% overhead. Most home upload speeds are far lower, which is why first backups often take days.
What is the difference between bandwidth and throughput?
Bandwidth is a link's maximum capacity; throughput is the rate actually achieved. Throughput is lower because of protocol headers, encryption, Wi-Fi conditions, congestion and server limits.