By Madan Kc, ISP/GPON engineer at DG Link Network · Updated 13 November 2026
1. Speed converter and data per hour, day and month
2. How long does a data cap or FUP last?
3. Uplink planning from contention ratio
Why 100 Mbps is not 100 MB/s
One byte is 8 bits. Line rates use bits and decimal prefixes (1 Mbps = 1,000,000 bits per second). Divide by 8 for bytes: 100 Mbps = 12.5 MB/s. Real downloads are slower because of protocol overhead, Wi-Fi and the server at the other end. A typical TCP download reaches roughly 90 to 95 percent of the line rate on a clean wired link. This tool uses decimal GB (1 GB = 1,000 MB), the way most ISPs and bills count data. Windows shows file sizes in binary units, so a file may look about 7 percent smaller than the quota used.
| Plan | MB/s | GB per hour | GB per day |
|---|---|---|---|
| 10 Mbps | 1.25 | 4.5 | 108 |
| 50 Mbps | 6.25 | 22.5 | 540 |
| 100 Mbps | 12.5 | 45 | 1,080 |
| 1 Gbps | 125 | 450 | 10,800 |
About contention ratio
A contention (or oversubscription) ratio of 8:1 means the sum of all sold plan speeds is eight times the uplink. There is no standard value. Residential ISPs often plan from 4:1 to 20:1 depending on the plan mix, the traffic and how much cached or local content they serve, and business or dedicated links use much lower ratios. Treat the result as a starting point and size from measured peak-hour traffic on your own network. Use the ISP bill calculator for the money side.
FAQ
How many MB/s is 100 Mbps?
100 Mbps is 12.5 MB/s, because there are 8 bits in a byte. Real transfers are usually a little lower.
How many GB can I download in a month at 50 Mbps?
At full speed 24 hours a day, 50 Mbps moves about 16,200 GB in 30 days. Nobody uses a line like that, so use the average-use field to model realistic usage.
What contention ratio should my ISP use?
There is no fixed rule. It depends on the plan mix and how busy the peak hour is. Measure peak-hour utilisation of your uplink and keep it below about 70 to 80 percent so you have room to grow.
Are GB here decimal or binary?
Decimal: 1 GB is 1,000 MB, which matches how ISPs count data. Binary GiB is about 7.4 percent larger.
Related
Sources and testing: Unit definitions are standard (SI prefixes, 8 bits per byte). Contention ratios are a commercial planning convention, not a standard, so the example values are starting points only.