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Calculate how long a transfer will take from file size and connection speed — with both file-size conventions and a realistic throughput figure, not just the theoretical maximum.
| NBN Plan | Download | 4GB file |
|---|---|---|
| NBN 25 (Basic) | 25 Mbps | — |
| NBN 50 (Standard) | 50 Mbps | — |
| NBN 100 (Fast) | 100 Mbps | — |
| NBN 250 (Superfast) | 250 Mbps | — |
| NBN 1000 (Ultrafast) | 1,000 Mbps | — |
| Metric | Value |
|---|
This one difference explains most bandwidth confusion. Internet speeds are sold in bits per second. Files are measured in bytes. There are eight bits in a byte.
The capital letter matters: Mb is megabit, MB is megabyte. A 100 Mbps connection is not "100 megabytes per second" — it is one eighth of that. This is why a download manager showing 11 MB/s on a 100 Mbps plan is working correctly, not underperforming.
| Plan speed | Theoretical MB/s | Realistic MB/s | 1 GB file takes |
|---|---|---|---|
| 25 Mbps | 3.13 | ~2.9 | About 6 minutes |
| 50 Mbps | 6.25 | ~5.8 | About 3 minutes |
| 100 Mbps | 12.5 | ~11.5 | About 1.5 minutes |
| 250 Mbps | 31.3 | ~28.8 | About 37 seconds |
| 1,000 Mbps | 125 | ~115 | About 9 seconds |
Here is the discrepancy nobody warns you about, and it is why your calculation and your download manager disagree.
| Binary (GiB) | Decimal (GB) | |
|---|---|---|
| 1 GB equals | 1,073,741,824 bytes | 1,000,000,000 bytes |
| Based on | Powers of two (1,024) | Powers of ten (1,000) |
| Used by | Windows file sizes, RAM | Storage vendors, macOS, network speeds |
| At 100 Mbps a 1 GB file takes | 1m 26s | 1m 20s |
The calculator above reports both, so you can see which figure matches whatever you are comparing against.
Even after the bits-to-bytes conversion, real transfers fall short of the theoretical maximum. The connection speed describes raw capacity; some of it carries the machinery of the transfer rather than your file.
| Overhead | Typical cost | What it is |
|---|---|---|
| TCP/IP headers | ~3–5% | Every packet carries addressing and sequencing information |
| Acknowledgements | ~2–3% | The receiver confirms each window of data |
| Retransmission | Variable | Lost packets are sent again |
| Encryption (TLS) | ~1–2% | Nearly all traffic is now encrypted |
| Wi-Fi contention | Up to 50% | Shared airtime, interference and distance |
A realistic figure for a wired connection is around 92% of line rate, which the calculator shows as its own row. Over wi-fi the gap is often much larger — and if your download seems slow, the wireless link is a far more likely culprit than the internet plan.
NBN plans are sold by speed tier, and the numbers that matter are not the headline ones.
| Tier | Download / upload | Suits |
|---|---|---|
| NBN 25 | 25 / 5 Mbps | One or two people, streaming and browsing |
| NBN 50 | 50 / 20 Mbps | The most common household choice |
| NBN 100 | 100 / 20 or 40 Mbps | Multiple heavy users, 4K streaming, working from home |
| NBN 250 | 250 / 25 Mbps | Large households, frequent big downloads |
| NBN 1000 | Up to 1,000 / 50 Mbps | Enthusiasts and heavy uploaders — availability is limited |
Australian retailers are required to advertise typical evening speeds — the throughput you can expect during the busy 7pm to 11pm period — rather than only the theoretical maximum. That figure is a far better guide than the tier name, because congestion in the evening is what most people actually experience.
Useful when you know what you are moving but not how big it is. Times assume the link is otherwise idle and running at full rate.
| File | Approx. size | at 50 Mbps | at 100 Mbps | at 1 Gbps |
|---|---|---|---|---|
| MP3 song, 4 min | 5 MB | 1 sec | 0 sec | 0 sec |
| Photo, 12 MP JPEG | 5 MB | 1 sec | 0 sec | 0 sec |
| RAW photo | 25 MB | 4 sec | 2 sec | 0 sec |
| Podcast episode | 60 MB | 10 sec | 5 sec | 1 sec |
| TV episode, HD | 2 GB | 4 min | 2 min | 13 sec |
| HD movie | 5 GB | 14 min | 7 min | 43 sec |
| 4K movie | 50 GB | 2.4 hrs | 1.2 hrs | 7 min |
| Windows update | 4 GB | 11 min | 6 min | 34 sec |
| macOS update | 12 GB | 34 min | 17 min | 2 min |
| AAA game | 120 GB | 5.7 hrs | 2.9 hrs | 17 min |
| Phone backup | 100 GB | 4.8 hrs | 2.4 hrs | 14 min |
| 1 hour 4K video footage | 300 GB | 14.3 hrs | 7.2 hrs | 43 min |
| Activity | Bandwidth | Notes |
|---|---|---|
| Web browsing, email | 1–5 Mbps | Negligible on any modern plan |
| Music streaming | ~0.3 Mbps | Even lossless audio is modest |
| Standard definition video | ~3 Mbps | Per stream |
| HD video (1080p) | ~5 Mbps | Per stream |
| 4K video | ~15–25 Mbps | Per stream — the figure most people overestimate |
| Video call (HD) | ~2–4 Mbps each way | Upload matters as much as download |
| Group video call | ~4–8 Mbps | Scales with participants shown |
| Online gaming | ~3–5 Mbps | Bandwidth is not the issue — latency is |
| Game downloads | As much as available | Modern titles run 50–150 GB |
What each service actually recommends, per simultaneous stream.
| Service and quality | Recommended |
|---|---|
| YouTube — 1080p HD | ~5 Mbps |
| YouTube — 4K | ~20 Mbps |
| Netflix — HD | ~5 Mbps |
| Netflix — 4K | ~15–25 Mbps |
| Disney+ — 4K | ~25 Mbps |
| Stan, Binge — HD | ~5 Mbps |
| Kayo — HD sport | ~6–8 Mbps |
| Spotify — very high quality | ~0.3 Mbps |
| Zoom, Teams — HD call | ~3–4 Mbps each way |
| Cloud gaming (GeForce Now, Xbox) | ~15–35 Mbps |
This is the most persistent misconception in the whole topic. Online games send tiny amounts of data very frequently. What matters is how fast each packet arrives, not how many could fit.
| Ping | Experience |
|---|---|
| Under 20 ms | Excellent — competitive play |
| 20–50 ms | Good — typical for an Australian server on fixed-line NBN |
| 50–100 ms | Playable; noticeable in fast-paced games |
| 100–150 ms | Typical to Asian or US West servers from Australia |
| Over 150 ms | Frustrating in anything requiring precision |
Upload is where Australian connections hurt, and the arithmetic is worth doing before you commit to a backup strategy.
| Data | at 20 Mbps up | at 40 Mbps up | at 50 Mbps up |
|---|---|---|---|
| 10 GB | ~1.2 hours | ~36 minutes | ~29 minutes |
| 100 GB | ~12 hours | ~6 hours | ~5 hours |
| 500 GB | ~2.5 days | ~1.3 days | ~1 day |
| 2 TB | ~10 days | ~5 days | ~4 days |
Assuming the link is otherwise idle and running at full rate, which it will not be. Practical advice: run the initial backup overnight or across a weekend, then let incremental backups handle the rest — after the first pass, daily changes are usually small. For genuinely large migrations, cloud providers offer physical shipping appliances precisely because uploading tens of terabytes is impractical.
| Type | Typical speed | Latency | Notes |
|---|---|---|---|
| Fibre (FTTP) | Up to 1,000 Mbps | Very low | Best available; symmetric options exist on business plans |
| FTTC / FTTN | 25–100 Mbps | Low | Speed depends on copper distance from the node |
| HFC (cable) | 100–1,000 Mbps | Low | Shared with the neighbourhood — evening congestion is common |
| 5G home internet | 50–500 Mbps | Low to moderate | Highly variable with tower distance and load |
| Fixed wireless | 25–100 Mbps | Moderate | Regional areas; weather can affect it |
| Satellite (LEO) | 50–200 Mbps | ~25–60 ms | Remote areas; far better latency than older satellite |
| Satellite (geostationary) | 12–25 Mbps | 600 ms+ | The 72,000 km round trip makes gaming and calls difficult |
Since wi-fi is usually the real bottleneck, it is worth knowing what yours can actually deliver. The headline figures below are aggregate maximums across all bands and streams — a single device typically sees a fraction of them.
| Generation | Standard | Bands | Headline max | Realistic single device |
|---|---|---|---|---|
| Wi-Fi 4 | 802.11n | 2.4 / 5 GHz | 600 Mbps | ~50–100 Mbps |
| Wi-Fi 5 | 802.11ac | 5 GHz | ~3.5 Gbps | ~200–400 Mbps |
| Wi-Fi 6 | 802.11ax | 2.4 / 5 GHz | ~9.6 Gbps | ~400–800 Mbps |
| Wi-Fi 6E | 802.11ax | + 6 GHz | ~9.6 Gbps | ~600–1,200 Mbps close range |
| Wi-Fi 7 | 802.11be | 2.4 / 5 / 6 GHz | ~46 Gbps | ~1–2 Gbps close range |
| Situation | What actually helps |
|---|---|
| Plan is 50 or 100 Mbps | Wi-Fi 5 is already faster than your connection. Upgrading the router changes nothing |
| Plan is 250 Mbps or more | Wi-Fi 6 or better is worth having, and so is a device that supports it |
| Many devices, crowded apartment | Wi-Fi 6 handles congestion far better than raw speed suggests — that is its main advantage |
| Weak signal in distant rooms | Mesh nodes or an access point on ethernet. No generation upgrade fixes range |
| Speed drops when someone streams | Airtime contention. Move heavy devices to 5 GHz or wire them |
How do I convert Mbps to MB/s?
Divide by eight, because there are eight bits in a byte. A 100 Mbps connection is 12.5 MB/s in theory and around 11.5 MB/s in practice once protocol overhead is accounted for. The capital letter matters: Mb is megabit, MB is megabyte.
How long does it take to download 100 GB?
At 100 Mbps, roughly 2.4 hours at theoretical speed and closer to 2.6 hours realistically. At 50 Mbps it is about 5 hours, and at 25 Mbps about 10 hours. Note that a "100 GB" file measured the Windows way is 7.4% larger than 100 decimal gigabytes, which adds several minutes at these sizes.
Why is my download slower than my plan speed?
Several reasons compound. Protocol overhead costs 6–10% before anything else. Wi-fi commonly costs far more than that. The server at the other end may be limiting you. A single download rarely saturates a fast connection because one TCP stream is limited by latency. And evening congestion affects shared connection types. Testing over ethernet separates a wireless problem from a connection problem.
What is the difference between bandwidth and speed?
Bandwidth is capacity — how much data the connection can carry at once. Speed is what you actually achieve, which is always lower. Latency is a third and separate thing: how long a single packet takes to make the round trip. A high-bandwidth connection with high latency feels slow for gaming and video calls despite downloading quickly.
Why does my 1 TB drive show as 931 GB?
The drive genuinely holds one decimal terabyte — 1,000,000,000,000 bytes. Windows divides by 1,024 three times rather than 1,000, arriving at about 931, but still labels the result "GB". Nothing is missing; the two systems simply count differently. The same discrepancy makes downloads take about 7.4% longer than a decimal calculation predicts.
How much bandwidth does Netflix use?
Around 3 Mbps for standard definition, 5 Mbps for HD and 15–25 Mbps for 4K, per simultaneous stream. Even a household running two 4K streams needs well under 100 Mbps. Streaming services also adapt quality to available bandwidth, so a temporarily slower connection reduces picture quality rather than stopping playback.
What internet speed do I need for gaming?
Very little — most games use 3 to 5 Mbps. What matters is latency, measured as ping. Under 20 ms is excellent, 20 to 50 ms is typical for an Australian server on fixed-line NBN, and over 150 ms is frustrating. Upgrading bandwidth does not reduce latency. Server distance, wi-fi and other devices saturating the link are the things worth addressing.
Why is my upload speed so much slower than download?
Most Australian NBN plans are deliberately asymmetric, because typical households download far more than they upload. A 100/20 plan uploads at a fifth of its download rate. This matters if you back up to cloud storage, send large files or run video calls — and upload speed improves very little between the 100 and 250 tiers, so check that figure specifically before upgrading.
How long will it take to back up my data to the cloud?
Divide your data by your upload speed, not your download speed. At 20 Mbps upload, 100 GB takes roughly 12 hours and 500 GB takes about two and a half days, assuming the link is otherwise idle. Run the initial backup overnight or across a weekend; incremental backups afterwards are usually small.
Is a gigabit plan worth it?
For most households, no. Two 4K streams, a video call and a game download together still fit inside 100 Mbps. Gigabit helps if you routinely move very large files, but wi-fi, the far-end server and single-connection limits often mean you never see the full rate anyway. Test over ethernet first — if your wired speed already matches your current plan, a faster tier will not fix a wireless bottleneck.
What is a typical evening speed?
It is the throughput an Australian retailer expects you to get during the busy 7pm to 11pm period, and providers are required to advertise it. It is a far more useful comparison than the tier name, because evening congestion is what most households actually experience. A plan with a lower headline speed but a higher typical evening speed may serve you better.
Does wi-fi slow down my internet?
Often substantially. Wi-fi is a shared medium where devices take turns, and throughput falls with distance, walls and interference. On a fast plan the wireless link is frequently the bottleneck rather than the connection itself. Testing the same download over ethernet is the quickest way to tell which one is limiting you.
Two adjustments turn an advertised speed into a realistic estimate: divide by eight to get bytes, then take off roughly 8% for protocol overhead. If the file size came from Windows, add another 7% because it is counting in binary while your connection is counting in decimal.
And when a connection feels slow, check wi-fi and latency before the plan — they are the usual culprits, and neither is fixed by paying for more bandwidth.
For the networking side of things, the IP subnet calculator covers address ranges and network planning, and the password generator creates credentials for the equipment you are configuring.