How long to download 5 GB at 100 Mbps

Five gigabytes at 100 Mbps is 400 seconds, or 6 minutes 40 seconds

Forty thousand megabits, divided once

One hundred megabits per second is 100,000,000 bits every second. Five decimal gigabytes hold 5,000 x 8 = 40,000 megabits. The division is one step: 40,000 / 100 = 400 seconds, and 400 seconds is 6 minutes 40 seconds.

Unit conversion confirms it. A 100 Mbps line delivers 100 / 8 = 12.5 megabytes per second, and 5,000 MB / 12.5 = 400. Each minute the line carries 750 MB, and each hour 45 GB.

Round numbers hide nothing, which is why this tier is easy to audit with a stopwatch: start a 5 GB transfer, and a finish near seven minutes confirms the line is doing what the label claims.

Because 100 is a round divisor, the rest of the ladder is mental arithmetic. One gigabyte takes 80 seconds, 10 GB takes 800 seconds, a 25 GB install takes 2,000 seconds, or 33 minutes 20 seconds, and a 250 MB phone update takes 20 seconds.

The short clock is why this tier feels different from the 25 Mbps plans it replaced. A film that took 26 minutes 40 seconds at 25 Mbps lands in 6 minutes 40 seconds here, and a 25 GB game install fits inside half an hour rather than two hours and thirteen minutes.

The 2024 federal benchmark is 100 Mbps down and 20 Mbps up

What the label covers, and what it leaves out

The number in this page's title is also a regulatory threshold. On 14 March 2024 the FCC adopted its Section 706 report and raised the fixed broadband benchmark from 25 Mbps down and 3 Mbps up to 100 Mbps down and 20 Mbps up, a fourfold increase on the download side. The same order set a long-term goal of 1 Gbps down with 500 Mbps up, according to the FCC announcement of the 2024 benchmark.

The benchmark describes what counts as advanced telecommunications capability when the agency judges deployment. It does not oblige a provider to deliver 100 Mbps at nine in the evening, and it says nothing about price. What it does control is the word broadband on a plan's marketing page.

Read the last two rows as a description of the entry tier. A 100/20 plan is exactly broadband by the 2024 definition and one tenth of the long-term download goal, which is why the same fiber line is sold at 500 Mbps or 1 Gbps a couple of years after installation.

The order also asked whether deployment was reasonable and timely, and the report counted about 24 million Americans without access to a 100/20 connection, concentrated in rural areas and on Tribal lands. That count describes coverage of a map, not the speed of any single line, and it is the reason the benchmark matters to funding decisions.

The practical effect for a download is small and the effect on shopping is large. A 100 Mbps plan is fast enough for this file and for a 4K stream at the same time; it is not a premium tier any more, and a sales page that presents it as one is using an old standard.

On a 100/20 plan the upload takes five times as long

Symmetry is the fiber feature that matters here

The 20 Mbps side of a 100/20 plan is where the asymmetry shows. Sending the same 5 GB file upstream takes 40,000 / 20 = 2,000 seconds, or 33 minutes 20 seconds, five times the download clock. With 6 percent overhead it becomes 2,120 seconds, or 35 minutes 20 seconds.

Many fiber providers sell symmetric tiers, where the upload matches the download. Cable plants usually reserve less capacity for the return path, which is why 100/20 and 300/20 are common shapes on coax and 100/100 or 500/500 are common on fiber. A symmetric 100/100 line returns the file in 400 seconds, the same as it takes to fetch it.

Coaxial plants split capacity between the forward and return paths, and DOCSIS tiers reflect that split. A network run by a municipal utility or a rural cooperative often sells the same rate in both directions because the equipment is provisioned that way. The plan name is a better guide than the technology label on the door.

The upstream number matters for backups and calls more than for downloads. A 100 GB backup at 20 Mbps is 800,000 / 20 = 40,000 seconds, or 11 hours 6 minutes 40 seconds; on a 100 Mbps upload the same backup is 8,000 seconds, or 2 hours 13 minutes 20 seconds.

Household calls add up on the narrow side. The FCC guide puts HD video teleconferencing at 6 Mbps, so three simultaneous calls use 18 of the 20 Mbps upstream and leave 2 Mbps for everything else, including the acknowledgements that keep the download moving. On a symmetric 100 Mbps upstream the same three calls leave 82 Mbps.

This is the case where a 100 Mbps plan can feel slow while a speed test reads 100. The download is fine; the upstream is queued, and a cloud photo sync or a game upload will sit behind the calls until it clears.

Four people at once still fit inside 100 Mbps

Two budgets, downstream and upstream

A 100 Mbps line has room for a family, but the budget has two sides and only one of them is generous on a 100/20 plan. Downstream demand is measured in streams and games; upstream demand is measured in calls, backups and photo syncs.

Two 4K streams at 15 Mbps each use 30 Mbps downstream and leave 70, so the file takes 40,000 / 70 = 571.4 seconds, or 9 minutes 31 seconds. Four 1080p streams use 20 Mbps, leave 80 and give 500 seconds, or 8 minutes 20 seconds. Add three HD calls at 6 Mbps each and 18 of the 20 Mbps upstream are committed, which is fine for the calls and tight for a phone backup running at the same time.

The last row is the one that produces support calls. Downstream demand of 79 Mbps leaves 21 Mbps, which stretches the file to 1,904.8 seconds, or 31 minutes 45 seconds, and upstream demand of 36 Mbps exceeds the 20 Mbps the plan provides. Every upload packet queues, so calls freeze and the file crawls even though the plan is delivering its rated download speed.

Telehealth appointments, photo libraries syncing to the cloud, and school tablets pulling lessons all draw on the same upstream allowance. None of them looks heavy alone; together they compete with the file, and the household calendar matters as much as the plan name on the bill.

The fix is scheduling rather than a bigger plan. Backups at two in the morning, one video call at a time, and a router that gives the call priority over the backup will keep the same line usable through an evening. A symmetric tier removes the upstream half of the problem for households that work from home.

A 1.2 TB allowance holds 240 copies of the file

Cap arithmetic and the hours behind it

A 1.2 TB monthly allowance is 1,200 GB, so 1,200 / 5 = 240 downloads of this file before the meter stops. Count the traffic that crosses the wire with 6 percent overhead and each copy costs 5.3 GB, which drops the count to 226.42.

Moving the whole allowance takes 1,200 GB x 8 = 9,600,000 megabits, so 9,600,000 / 100 = 96,000 seconds, or 26 hours 40 minutes, roughly 1.1 days of flat out transfer. Sending it upstream at 20 Mbps takes 480,000 seconds, or 133 hours 20 minutes, which is 5.6 days.

Spread over a month the allowance is 40 GB a day. At 100 Mbps that is 53 minutes 20 seconds of full rate transfer per day, so a household that exhausts 1.2 TB is not downloading films. It is streaming, and section 4 shows how quickly two 4K screens turn into 30 Mbps of continuous demand.

Enforcement is thin. The benchmark shapes marketing and federal funding decisions; it does not create a refund when a line measures 60 Mbps at peak, and overage fees or throttling are governed by the provider's own terms. Read the contract, not the headline speed.

Allowances differ by provider and by market, and some plans have none. The arithmetic above works for any figure: replace 1.2 TB with your own number and divide by the file size on the wire, which is the file size times 1.06 at 6 percent overhead.

Advertised 100, measured 87: the gap is documented

The FCC Measuring Broadband America data

The FCC tests delivered speed against advertised speed every year. Its Thirteenth Measuring Broadband America report, published on 9 August 2024 from data collected in September and October 2022, found a weighted average advertised download speed of 467 Mbps across participating providers. Eight of the twelve provider and technology pairs delivered at or above 100 percent of advertised speed during peak hours, defined as 7 to 11 pm local time, and the other four delivered 86 to 90 percent.

The same report gives a percentile view: for 95 percent of subscribers, cable minimums ran 73 to 95 percent of advertised speed, while fiber ran 84 to 103 percent. Those ranges describe the slow end of each provider's customer base, not the average line.

The clock moves less than the worry suggests. A line at 87 percent of advertised still finishes this file in 7 minutes 40 seconds, one minute longer than the sticker figure. On a 60 GB game the same 13 percent gap costs 624 seconds, or 10 minutes 24 seconds, which is when the shortfall starts to matter.

The sample comes from volunteers with panel hardware, so it describes the providers that chose to take part rather than the whole market. Treat the percentages as a floor for the industry, not a promise about your address.

Pick a weekday and repeat the test at noon and at nine; the pair of readings says more about your segment than any single sample.

Providers overprovision as a rule, so a 100 Mbps tier often tests above 100 on a quiet line and lands near 87 only at peak. If a line measures 87 at eight in the evening and 100 at noon, the plan is behaving as designed and the gap is congestion on the shared segment, not a provisioning error.

The binary reading adds 29 seconds, big files add hours

5 GiB, a 60 GB game and a 100 GB backup

Windows reports file size in gibibytes, where one GiB is 1,073,741,824 bytes, while line speed is sold in decimal bits. A file that Windows calls 5.00 GB is usually 5 GiB. The chain is 5 x 1,073,741,824 = 5,368,709,120 bytes, which is 42,949,672,960 bits, and 42,949,672,960 / 100,000,000 = 429.4967296 seconds, or 7 minutes 9 seconds.

That is 29.5 seconds more than the decimal result, a gap of 7.37 percent, which is 1.024 cubed. The NIST note on binary prefixes explains why both readings exist. Add 6 percent overhead and the binary job reaches 455.27 seconds, or 7 minutes 35 seconds.

File Explorer and most backup tools show gibibytes, while a publisher's download page quotes decimal gigabytes, so one label can describe two different byte counts. The mismatch is a naming convention, not a missing gigabyte.

The larger the file, the more the small percentages cost. A 60 GB game is 480,000 megabits, so 4,800 seconds at 100 Mbps, or 1 hour 20 minutes; 6 percent overhead pushes it to 5,088 seconds, or 1 hour 24 minutes 48 seconds, and the 7.37 percent binary gap is another 353.8 seconds, close to six minutes.

A 100 GB backup set is 8,000 seconds, or 2 hours 13 minutes 20 seconds, and 8,480 seconds with overhead. A 20 GB patch is 1,600 seconds, or 26 minutes 40 seconds. A 700 MB episode is 56 seconds, and at that size the difference between decimal and binary is under four seconds, which is why the 5 GB file is a reasonable place to argue about it and a phone update is not.