Have you ever found yourself calculating how long your online backups will take to complete? Understanding how long online backups take is crucial for managing your backup schedules and setting realistic expectations. This guide provides insights into calculating backup durations based on various factors.

Understanding Data Transfer Rates

using bandwidth helps in calculating how long backups will takeA key factor in determining backup time is the data transfer rate of your internet connection. We provide a comprehensive table showing theoretical best-case data transfer rates for different types of connections like T1s, DS1s, and OC3s.

Theoretical Data Transfer Rates Table

The following table shows theoretical best-case data transfers rates (GB/Hr and GB/Day) for different speed Internet connections – where you can interpolate additional values when you know the speed of a specific user’s Internet connection:

kbps mbps KBs MBs Name #GB/hour #GB/day
64 0.063 8 0.008 0.03 0.66
128 0.125 16 0.016 0.05 1.32
256 0.250 32 0.031 0.11 2.64
384 0.341 48 0.043 0.15 3.60
512 0.512 64 0.064 0.23 5.40
756 0.772 95 0.097 0.34 8.14
1,581 1.544 198 0.193 T1/DS1 0.68 16.28
5,120 5.000 640 0.625 2.20 52.73
6,463 6.312 808 0.789 T2/DS2 2.77 66.57
10,240 10.000 1,280 1.250 4.39 105.47
45,810 44.736 5,726 5.592 T3/DS3 19.66 471.83
51,200 50.000 6,400 6.250 21.97 527.34
102,400 100.000 12,800 12.500 43.95 1,054.69
158,106 154.400 19,763 19.300 OC3 67.85 1,628.44
204,800 200.000 25,600 25.000 87.89 2,109.38
280,756 274.176 35,095 34.272 DS4 120.49 2,891.70
632,422 617.600 79,053 77.200 OC12 271.41 6,513.75
1,024,000 1,000.000 128,000 125.000 1Gbs 439.45 10,546.88
2,529,690 2,470.400 316,211 308.800 OC48 1,085.63 26,055.00
10,118,758 9,881.600 1,264,845 1,235.200 OC192 4,342.50 104,220.00

Real-World Internet Speeds

Internet Service Providers (ISPs) may advertise certain speeds, but the actual speed during sustained TCP connections, like backups, can be different. We discuss how to realistically estimate backup time given these variables. But what is the client’s actual Internet speed?  Is the rate that the ISP publishes real?  It appears that some major ISPs are now allowing their client’s to burst to higher bandwidth speeds for short periods of time and then the ISP throttles the connection for sustained TCP connections (such as for your client’s backups and restores), and thus connection test speeds and (tested) ISP advertised speeds may not accurately reflect reality.  Given this, how can one actually estimate how long a backup with take and what their actual Internet bandwidth is?

Testing Your Actual Internet Speed

Learn how WholesaleBackup clients can test their actual upload and download speeds to backup servers, ensuring a more accurate backup time estimation. WholesaleBackup clients can test their actual upload and download speed to your backup servers from the software client on the “Remote Settings” tab!  Furthermore, WholesaleBackup clients can also throttle their connection speed to your servers on the “Remote Settings” tab.

Factors Affecting Backup Duration

server volume performance and disk write times

In practice, backups take longer than theoretical maximums due to integrity checks, compression, encryption, and latency. We explain how these factors impact backup duration. In practice, an online backup will take longer than the theoretical maximums above due to the time to perform integrity checks, compression, encryption, and differentials as well as the latency of their Internet connection.  WholesaleBackup’s offsite backup software provides an estimate (on the “Monitor” tab) of the time it will take to perform the backup, it is basically a worst-case estimate, and as one watches it one will see that, as time passes, the throughput typically improves dramatically and the estimated completion time gets better – this is due to optimizations we perform as the backup proceeds and the fact that its backs up the client’s largest files last and these make the best use of their Internet pipe.

Optimizing Backup Performance

Discover strategies to optimize the backup process, including prioritizing larger files and utilizing the software’s inbuilt optimization features. Another related question, covered in a previous blog post entitled “Sizing your Internet Pipe for Your Online Backup Business” on, is how to calculate, from real-world experience, how much Internet bandwidth is required to run your own online backup business.


Estimating online backup duration is a blend of understanding theoretical speeds and considering real-world variables. This guide aims to provide a comprehensive overview to help you manage your online backup process more efficiently.

Online Backup Business Guide