Download Time Calculator
Calculate download time for any file size and internet speed. Convert between bandwidth units (Mbps, MB/s, KB/s) and see how long downloads take at different speeds.
Download Time
Estimated time
1m 20s
1 GB at 100 Mbps
File size (bytes)
1,000,000,000
File size (bits)
8,000,000,000
Speed (Mbps)
100.000 Mbps
Speed (MB/s)
12.500 MB/s
Download Time by Connection Type
| Connection | Speed | Time for 1 GB |
|---|---|---|
| Dial-up | 0.056 Mbps | 1d 16h |
| 3G Mobile | 5 Mbps | 26m 40s |
| 4G LTE | 30 Mbps | 4m 27s |
| DSL 25 Mbps | 25 Mbps | 5m 20s |
| Cable 100 Mbps | 100 Mbps | 1m 20s |
| Wi-Fi 5 (300 Mbps) | 300 Mbps | 26.7 seconds |
| Fiber 1 Gbps | 1 Gbps | 8.0 seconds |
| 5G (1 Gbps) | 1 Gbps | 8.0 seconds |
How to Use Download Time Calculator
- 1Enter the file size in your preferred unit (KB, MB, GB, TB).
- 2Enter your internet speed in Mbps, MB/s, or other units.
- 3View the estimated download time and see how it compares across connection types.
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Frequently Asked Questions
Why is download speed in Mbps different from MB/s?▾
Mbps (megabits per second): used by ISPs to advertise speed. 1 Mbps = 1,000,000 bits/second. MB/s (megabytes per second): used by file managers and download managers. 1 MB/s = 8 Mbps. To convert: divide Mbps by 8. Example: 100 Mbps internet = 12.5 MB/s maximum download speed. A 1 GB file at 100 Mbps takes 80 seconds (1 GB = 8 Gb, 8,000 Mb ÷ 100 Mbps = 80s). ISPs use bits because the numbers look bigger. Storage is measured in bytes. This "bit vs byte" confusion is intentional marketing.
Why does actual download speed differ from advertised speed?▾
Advertised vs actual speed differences: ISPs advertise maximum theoretical speed; real speed depends on: network congestion (peak hours), Wi-Fi vs Ethernet (Wi-Fi adds overhead and signal loss), number of simultaneous users, distance from fiber node or cell tower, server-side throughput limits, and TCP/IP overhead (~3-5%). Real-world rule of thumb: assume 60-80% of advertised speed. Protocol overhead: HTTP/2 and QUIC are more efficient than HTTP/1.1. CDN servers are faster than origin servers for large downloads.
What are typical internet speeds by connection type?▾
Dial-up: 56 Kbps (0.056 Mbps). DSL basic: 1-25 Mbps down. Cable: 25-1,000 Mbps down. Fiber: 100-10,000 Mbps (10 Gbps). 3G mobile: 0.5-5 Mbps. 4G LTE: 10-100 Mbps (average ~30 Mbps). 5G: 50-1,000 Mbps (millimeter wave: up to 10 Gbps). Wi-Fi 5 (802.11ac): up to 3.5 Gbps theoretical. Wi-Fi 6 (802.11ax): up to 9.6 Gbps theoretical. Starlink satellite: 25-220 Mbps. As of 2025, median US household speed is ~250 Mbps.
How do I calculate file transfer time over a network?▾
Transfer time = File size (bits) / Transfer rate (bits per second). Convert everything to the same unit: 1 byte = 8 bits. Example: 500 MB file at 50 Mbps: 500 MB = 4,000 Mb; 4,000 Mb / 50 Mbps = 80 seconds = 1 minute 20 seconds. For TCP over the internet, subtract protocol overhead (~5%), and account for latency: large files in small chunks over high-latency connections take longer even with high bandwidth (bandwidth-delay product). SSH/SCP is often faster than FTP due to lower overhead.
What is the bandwidth-delay product?▾
Bandwidth-delay product (BDP) = bandwidth × round-trip time (RTT). It measures the amount of data "in flight" in the network at any time. Example: 1 Gbps link with 100ms RTT = 100 megabits = 12.5 MB of data in transit. TCP requires the receive window to be at least BDP-sized to fully utilize the link. With default TCP window size of 64 KB, a 100ms RTT link maxes out at ~5 Mbps regardless of bandwidth. TCP window scaling (RWIN) and modern congestion control (CUBIC, BBR) address this for long-distance high-bandwidth links.