Why are bits (Mbps) and bytes (MB/s) different?

Internet connection speeds are advertised in bits per second (Mbps). Files are measured in bytes. 1 byte = 8 bits, so 100 Mbps = 12.5 MB/s in theory and ~11 MB/s after overhead.

What's the difference between MB and MiB?

Decimal (SI): MB = 1,000,000 bytes. Binary (IEC): MiB = 1,048,576 bytes. Storage marketers use decimal; operating systems often use binary. Pick whichever matches your source.

Is the overhead slider accurate?

It's a flat-percentage approximation. Real overhead depends on protocol (HTTP/2, QUIC, raw TCP), packet loss, RTT, and parallelism. 5 % is reasonable for fast LAN, 10–15 % for high-RTT or lossy links.

Does this work for upload too?

Yes — the math is the same. Just enter your upload speed instead of download speed.

Bandwidth & Download Time Calculator

Network

Compute any one of (transfer time, required throughput, transferable size) from the other two. Useful for sizing downloads on a slow connection, validating a backup window, estimating CDN cost, or sanity-checking a 'how long will this take' question. Bit-rate units (Mbps, Gbps) and byte-rate units (MB/s) are kept distinct — and decimal (KB = 1000) vs binary (KiB = 1024) prefixes are both supported. An overhead slider models the ~5–10 % loss from TCP/IP headers, ACKs, and framing.

—

Solve for

File size

Connection speed

Protocol overhead: 5%Approximate TCP/IP framing & retransmit loss. 5 % is typical for fast LAN, 10–15 % for high-latency links.

Speed presets

Estimated transfer time

6m 35s

Effective rate (bits/s):95.0 Mbps

Effective rate (bytes/s):11.9 MB/s

Decimal units (KB = 1000) and binary units (KiB = 1024) are both available — pick the one your source uses.

How to use

Pick a mode: solve for time, required speed, or transferable size.
Enter the two known values with units; the third updates live.
Use a connection preset (Wi-Fi 6, Gigabit, 4G LTE…) to fill in a typical speed.

Frequently asked questions

Why are bits (Mbps) and bytes (MB/s) different?: Internet connection speeds are advertised in bits per second (Mbps). Files are measured in bytes. 1 byte = 8 bits, so 100 Mbps = 12.5 MB/s in theory and ~11 MB/s after overhead.
What's the difference between MB and MiB?: Decimal (SI): MB = 1,000,000 bytes. Binary (IEC): MiB = 1,048,576 bytes. Storage marketers use decimal; operating systems often use binary. Pick whichever matches your source.
Is the overhead slider accurate?: It's a flat-percentage approximation. Real overhead depends on protocol (HTTP/2, QUIC, raw TCP), packet loss, RTT, and parallelism. 5 % is reasonable for fast LAN, 10–15 % for high-RTT or lossy links.
Does this work for upload too?: Yes — the math is the same. Just enter your upload speed instead of download speed.

Related tools

IP Address Inspector

Type an IPv4 or IPv6 address and see its class, scope (private / public / loopback / link-local), decimal value, binary, reverse-DNS notation, and /32 CIDR.

Network00

Port Number Reference

Searchable cheat sheet for ~60 standard TCP / UDP port numbers — from 22 (SSH) and 80 (HTTP) to 6379 (Redis) and 27017 (MongoDB).

Network00

DNS Record Reference

Searchable cheat sheet for DNS record types — A, AAAA, CNAME, MX, TXT, NS, SOA, PTR, SRV, CAA, DNSSEC, SVCB / HTTPS — with examples.

Network00

Subnet Calculator (IPv4 / CIDR)

Parse an IPv4 CIDR into network address, broadcast, netmask, wildcard, host range, and class. Shows binary breakdown and private/public status.

Network00

User Agent Parser

Parse a User-Agent string into browser, engine, OS, device, and CPU. Detects 20+ bots including GPTBot, ClaudeBot, PerplexityBot.

Network00

HTTP Status Code Reference

Searchable list of every HTTP status code (1xx-5xx) with summary, RFC, when to use, and common pitfalls.

Network00