Data Transfer Speed Calculator
Calculate how long it will take to download or upload a file. Three tiers: Quick, Extended with SA ISP comparison and streaming quality checker, and Professional with parallel downloads, protocol overhead, and VPN throughput impact.
| Connection | Time |
|---|---|
| Fibre (entry, 25 Mbps) | 5 min 44 sec |
| Fibre (standard, 100 Mbps) | 1 min 26 sec |
| Fibre (fast, 200 Mbps) | 42.9 seconds |
| Fibre (gigabit, 1 Gbps) | 8.6 seconds |
| LTE (average ~25 Mbps) | 5 min 44 sec |
| ADSL (8 Mbps) | 17 min 54 sec |
| USB 3.0 | 1.7 seconds |
Theoretical maximum speeds shown. Real-world speeds are typically 60–90% of rated capacity due to protocol overhead, network congestion, and hardware limitations.
How to Use This Calculator
Enter your file size and select the unit (KB, MB, GB, TB), then enter your connection speed and unit. The download time calculates instantly. The comparison table shows estimated times across common South African connection types.
Important: ISP speeds are in Megabits per second (Mbps), while file sizes are in Megabytes (MB). There are 8 bits in a byte, so a 100 Mbps connection transfers 12.5 MB per second (100 ÷ 8 = 12.5).
The Extended Calculator shows SA ISP speed comparisons and streaming quality requirements. The Professional Calculator adds parallel download estimation, protocol overhead, and VPN impact by server location.
| Provider / Plan | Down (Mbps) | vs yours |
|---|---|---|
| Openserve ADSL (4Mbps) | 4 | 25.0× slower |
| Openserve VDSL (20Mbps) | 20 | 5.0× slower |
| Vumatel Fibre 25/25 | 25 | 4.0× slower |
| Vumatel Fibre 100/100 | 100 | 1.0× |
| Vumatel Fibre 200/200 | 200 | 2.0× |
| Vodacom 5G (peak) | 500 | 5.0× |
| MTN 5G (urban peak) | 300 | 3.0× |
| MTN 4G LTE | 50 | 2.0× slower |
| Vodacom 4G LTE | 40 | 2.5× slower |
| Rain 5G Home (typical) | 50 | 2.0× slower |
Mbps vs MB/s Explained
100 Mbps fibre = 12.5 MB/s actual file transfer speed
Download time = File size (bits) ÷ Speed (bps)
Example: 4 GB file on 100 Mbps = (4 × 1 024 × 1 024 × 1 024 × 8) bits ÷ 100 000 000 bps ≈ 343 seconds ≈ 5 min 43 sec
SA Internet Speed Context
| Connection Type | Typical Speed | MB/s |
|---|---|---|
| ADSL | 4–8 Mbps | 0.5–1 MB/s |
| LTE (4G average) | 20–50 Mbps | 2.5–6 MB/s |
| 5G (urban areas) | 100–500 Mbps | 12–62 MB/s |
| Fibre (entry) | 25–50 Mbps | 3–6 MB/s |
| Fibre (standard) | 100–200 Mbps | 12–25 MB/s |
| Fibre (gigabit) | 1 000 Mbps | 125 MB/s |
| Unit | Value |
|---|---|
| bps | 100 000 000 |
| Kbps | 100 000 |
| Mbps | 100 |
| Gbps | 0,1 |
| KB/s | 12 500 |
| MB/s | 12,5 |
| GB/s | 0,013 |
Parallel Download Estimator
Protocol Overhead Calculator
| Protocol | Overhead | Effective (100 Mbps raw) |
|---|---|---|
| HTTP/1.1 | 3% | 97 Mbps |
| HTTP/2 | 1.5% | 98,5 Mbps |
| HTTP/3 (QUIC) | 1% | 99 Mbps |
| FTP | 5% | 95 Mbps |
| SFTP (SSH) | 8% | 92 Mbps |
| HTTPS (TLS 1.3) | 2.5% | 97,5 Mbps |
| WireGuard VPN | 3.5% | 96,5 Mbps |
| OpenVPN | 10% | 90 Mbps |
| IPSec VPN | 6% | 94 Mbps |
VPN Speed Impact by Server Location
| VPN Location | Drop | Effective |
|---|---|---|
| Cape Town (local) | -0% | 100 Mbps |
| Johannesburg (local) | -2% | 98 Mbps |
| Nairobi, Kenya | -8% | 92 Mbps |
| London, UK | -25% | 75 Mbps |
| Amsterdam, NL | -28% | 72 Mbps |
| New York, USA | -35% | 65 Mbps |
| Los Angeles, USA | -40% | 60 Mbps |
| Tokyo, Japan | -45% | 55 Mbps |
| Sydney, Australia | -30% | 70 Mbps |