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Bandwidth Calculator,
download times in seconds.
Calculate exactly how long it takes to transfer any file — from a 10 MB photo to a 1 TB backup — over any connection speed. Supports Mbps, MB/s, Gbps, and KB/s. Accounts for network overhead and shows a comparison across common connection types.
Inputs
File & connection
10% is typical for real-world downloads. Use 0% for theoretical max.
Mbps = megabits/s (lowercase b) — internet speeds
MB/s = megabytes/s (uppercase B) — file transfer
1 MB/s = 8 Mbps · 100 Mbps = 12.5 MB/s
Transfer time
4 GB · 100 Mbps · 10% overhead
5m 56s
Theoretical: 5m 20s · +10% overhead
Days
00
Hours
00
Minutes
05
Seconds
56
Speed breakdown
Bits vs. bytes at a glance
Link speed
100 Mbps
advertised
Effective
90 Mbps
−10% overhead
In MB/s
11.25 MB/s
bytes per second
File size
4.00 GB
32.00 Gb
Connection comparison
How long on each connection?
| Connection | Speed | Transfer time |
|---|---|---|
| 3G mobile | 5 Mbps | 1h 58m 32s |
| 4G LTE | 30 Mbps | 19m 46s |
| Cable 100 Mbps | 100 Mbps | 5m 56s |
| 5G (mid-band) | 200 Mbps | 2m 58s |
| Fiber 500 Mbps | 500 Mbps | 1m 12s |
| Gigabit fiber | 1 Gbps | 36s |
| USB 3.0 | 5 Gbps | 8s |
Speeds shown are Mbps (megabits per second). Your row is highlighted in amber. Actual speeds depend on server capacity, Wi-Fi signal, and network congestion.
Bandwidth guide
Mbps vs. MB/s: the confusion that costs you time.
The single most common source of confusion in internet speeds is the difference between a lowercase b and an uppercase B. Internet service providers advertise speeds in Mbps (megabits per second). Your download manager shows progress in MB/s (megabytes per second). These are not the same unit and the math explains why your “100 Mbps” plan maxes out at around 12 MB/s in your browser.
Bits and bytes: the fundamental distinction
The convention exists for historical reasons: data storage was always measured in bytes (you buy a 1 TB hard drive, not an 8 Tb hard drive), while data transmission hardware was engineered around serial bit streams, so engineers measured line capacity in bits per second. Both conventions stuck, and users pay the confusion tax every time they look at a download bar.
Typical real-world internet speeds — ISP vs. achieved
Advertised speeds are the theoretical maximum under ideal conditions. Real-world speeds are lower due to signal attenuation, shared bandwidth at the ISP level, router overhead, and distance from cell towers or exchange nodes.
| Connection type | Advertised | Typical achieved | In MB/s (achieved) |
|---|---|---|---|
| 3G mobile | ~10 Mbps | 3–8 Mbps | 0.4–1.0 MB/s |
| 4G LTE | ~150 Mbps | 20–50 Mbps | 2.5–6.3 MB/s |
| 5G (sub-6 GHz) | 100–500 Mbps | 80–200 Mbps | 10–25 MB/s |
| 5G (mmWave) | 1–4 Gbps | 200–600 Mbps | 25–75 MB/s |
| Cable (DOCSIS 3.1) | 500–1,000 Mbps | 100–500 Mbps | 12.5–62.5 MB/s |
| DSL | 5–100 Mbps | 10–40 Mbps | 1.25–5 MB/s |
| Fiber (FTTH 1G) | 1,000 Mbps | 800–950 Mbps | 100–119 MB/s |
| Fiber (FTTH 10G) | 10 Gbps | 2–5 Gbps | 250–625 MB/s |
Network overhead — why you never get 100% of your plan speed
Even if your router negotiates the full link rate with your ISP, several layers of overhead consume bandwidth before a single byte of file data reaches your application:
- TCP/IP headers: Every packet carries addressing, sequencing, and checksum data. For typical 1,500-byte ethernet frames, headers consume roughly 3–5% of capacity.
- Acknowledgement packets: TCP requires the receiver to confirm receipt of each window of data. These “ACK” packets travel in the opposite direction but still occupy bandwidth on the return path.
- Retransmissions: Any lost or corrupted packet is resent, effectively doubling the bandwidth cost for that packet. On a congested network this can add 5–10% overhead or more.
- Protocol overhead: HTTPS adds TLS handshakes. VPNs add encryption headers (WireGuard is lean; OpenVPN is not). HTTP/2 multiplexing adds framing bits per stream.
- Wi-Fi overhead: 802.11 protocols include frame headers, CSMA/CA collision-avoidance wait times, and acknowledgement frames. Wi-Fi throughput is typically 50–70% of the theoretical channel capacity.
A combined overhead of 10% is a conservative, realistic default for a wired connection on an unloaded network. Wi-Fi on a shared network may add 15–25% overhead.
Common file sizes — what are you actually downloading?
| File type | Typical size | At 100 Mbps | At 1 Gbps |
|---|---|---|---|
| Email with attachment | 5 MB | 0.4s | < 0.1s |
| MP3 album | 100 MB | 9s | 1s |
| HD movie (1080p) | 4 GB | 5m 56s | 35s |
| 4K movie (H.265) | 15 GB | 22m | 2m 13s |
| PC game (AAA) | 50–100 GB | 1–2h | 7–14m |
| OS backup | 50 GB | 1h 7m | 7m |
| Hard drive backup | 1 TB | 22h | 2h 13m |
| Virtual machine image | 20 GB | 26m | 2m 48s |
Times assume 10% overhead. Actual times vary based on server speed and network conditions.
SI vs. binary prefixes — why 1 GB isn't always 1 GB
This calculator uses SI (decimal) prefixes: 1 MB = 1,000,000 bytes, 1 GB = 1,000,000,000 bytes, the same convention used by hard drive manufacturers and most modern operating systems when reporting storage capacity. However, some older operating systems (notably Windows before Windows 10) displayed storage in binary prefixes (also called mebibytes/gibibytes): 1 MiB = 1,048,576 bytes (2²⁰). This is why a 500 GB hard drive showed as ~465 GB in older Windows — the hardware used decimal GB but the OS displayed binary GiB.
For bandwidth purposes, ISPs always use decimal prefixes, so this calculator uses decimal throughout for consistency.