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Kalcufy

Bandwidth Calculator

What Is Bandwidth?

Bandwidth is the maximum rate at which data can be transferred over a network connection, measured in bits per second (bps) and its multiples. It represents capacity, not speed — think of it as the width of a pipe through which data flows. A wider pipe (more bandwidth) allows more data to pass at once. Internet Service Providers (ISPs) advertise speeds in megabits per second (Mbps), but file sizes are measured in megabytes (MB). Since 1 byte = 8 bits, a 100 Mbps connection can transfer at most 12.5 MB per second under ideal conditions. Real-world throughput is lower due to protocol overhead (TCP/IP headers), latency, congestion, and the difference between the physical link rate and usable application bandwidth.

Bits vs Bytes — Why the Confusion?

The endless confusion between Mbps and MB/s comes from the bit/byte distinction. A bit (b, lowercase) is a single binary digit (0 or 1). A byte (B, uppercase) is 8 bits. Network equipment and ISPs measure bandwidth in bits per second (bps, Kbps, Mbps, Gbps), while operating systems and file managers display file sizes in bytes (KB, MB, GB). This means a '100 Mbps' connection downloads files at about 12.5 MB/s, not 100 MB/s. Additionally, there are two competing standards for prefixes: decimal (SI, where 1 KB = 1,000 bytes) and binary (IEC, where 1 KiB = 1,024 bytes). Most networking uses decimal prefixes, while RAM and some storage uses binary. This calculator uses decimal (SI) prefixes, which is the networking standard.

Frequently Asked Questions

What is the difference between Mbps and MB/s?

Mbps (megabits per second) and MB/s (megabytes per second) measure data rate but in different units. Since 1 byte = 8 bits, you divide Mbps by 8 to get MB/s. A 100 Mbps internet plan gives you about 12.5 MB/s actual download speed. ISPs use Mbps because the larger number looks better in marketing, while your computer shows file downloads in MB/s.

Why is my actual download speed lower than my plan speed?

Several factors reduce real-world throughput: TCP/IP protocol overhead (3–5%), Wi-Fi signal loss (20–50% reduction vs wired), network congestion during peak hours, distance from the router, and ISP throttling. A 100 Mbps wired connection typically delivers 90–95 Mbps, while the same plan over Wi-Fi might deliver 50–80 Mbps depending on conditions.

How much bandwidth does streaming video require?

Netflix and YouTube recommend: SD (480p) = 3 Mbps, HD (1080p) = 5 Mbps, 4K UHD = 25 Mbps per stream. Multiple simultaneous streams add up — a household with 3 people streaming 4K needs about 75 Mbps just for video. Gaming adds 3–6 Mbps per player, and video calls need 1.5–4 Mbps each.

How do I calculate website hosting bandwidth?

Multiply monthly page views by average page size to get monthly data transfer. Then divide by seconds in a month (2,592,000) to get the average bandwidth in bytes per second. Multiply by 8 to convert to bits per second. Add a redundancy factor of 1.5–2x for traffic spikes and bot traffic. Example: 50,000 views × 2 MB = 100 GB/month = ~0.31 Mbps average, or ~0.62 Mbps with 2x redundancy.

What is the difference between bandwidth and throughput?

Bandwidth is the theoretical maximum capacity of a link — like the speed limit on a highway. Throughput is the actual amount of data successfully delivered — like how fast your car actually moves in traffic. Bandwidth is always higher than throughput because of protocol overhead, congestion, errors, and retransmissions. A 1 Gbps Ethernet link typically achieves 940–960 Mbps throughput.

Does bandwidth use decimal (1000) or binary (1024) prefixes?

Networking uses decimal (SI) prefixes: 1 Kbps = 1,000 bps, 1 Mbps = 1,000,000 bps, 1 Gbps = 1,000,000,000 bps. Storage traditionally uses binary: 1 KiB = 1,024 bytes. This creates a ~2.4% discrepancy at megabyte scale and ~7.4% at gigabyte scale. This calculator uses decimal (SI) standard, consistent with networking conventions and ISP measurements.