Streaming data is bitrate multiplied by time, and nothing else
A video stream is a pipe delivering a fixed number of bits every second. Multiply that rate by how long the pipe stays open and you have the total, exactly. Resolution, screen size and the show you picked change your data use only through their effect on bitrate: a 4K nature documentary and a 4K sitcom on the same service at the same quality setting cost you close to the same gigabytes per hour, because the encoder is targeting the same rate.
The conversion has three constants in it. There are 3,600 seconds in an hour. There are 8 bits in a byte, which is why a 16 Mbps stream is not 16 megabytes per second. And there are 1,000 megabytes in the gigabyte your internet provider meters — a decimal gigabyte, not the 1,024-based unit that your operating system calls a GB and that IEC 80000-13 properly names a gibibyte. Chain those together and one Mbps sustained for one hour is 0.45 GB. Everything else on this page is that number scaled up.
The reason this matters is that data caps are still common and still enforced. Several large United States cable providers apply a 1.2 TB monthly allowance — 1,229 GB in the decimal units they bill in — and sell overage in fixed blocks. Satellite and fixed-wireless plans meter far more tightly, and a phone plan's hotspot allowance is a separate, much smaller number printed in the plan terms rather than on the marketing page. On any of those plans, whether 4K is affordable is an arithmetic question, and this calculator answers it.
Working through the formula term by term
Start with the bitrate B in megabits per second. This is the only input you genuinely need to be accurate about, and it is the one people guess wrong most often, because services advertise the peak bitrate a title can reach while billing you for the average the stream actually sustains. If your player has a diagnostics overlay, watch it for a minute or two and take a mid-range figure rather than the highest number you see.
Multiply by 3,600 to get megabits per hour. Divide by 8 to get megabytes per hour, because network rates are quoted in bits and storage in bytes — a distinction that costs you a factor of eight if you drop it, and by far the most common error in a back-of-envelope estimate. Divide by 1,000 to get gigabytes. The three constants collapse into a single multiplier: GB per hour = 0.45 × Mbps.
Two adjustments follow. Simultaneous streams multiply the whole thing: two people watching different 4K titles at once use twice the data of one, even though they are watching for the same wall-clock hours. And audio-only listening runs on the same equation with kilobits instead of megabits, so 160 kbps is 0.16 Mbps, which is 0.072 GB per hour — light enough that music rarely threatens a cap unless you stream lossless, where 1,411 kbps works out to 0.635 GB per hour.
The month is taken as 30.44 days, which is 365.25 ÷ 12, so a per-day habit converts to a per-month total without the answer depending on whether the month you land in has 28 days or 31. Everything your household does that is not streaming — game downloads, cloud backup, video calls, updates, browsing — is entered as one monthly lump, because those are bursty and you already have last month's real figure in your provider's usage meter.
Worked example: 4K for three and a half hours a day on a 1,229 GB cap
A household streams 3.5 hours of 4K video a day on one screen, listens to 2 hours a day of music at 160 kbps, and used 50 GB last month on everything else. The plan carries a 1.2 TB cap, entered as 1,229 GB, with overage sold at $10 per 50 GB block.
- Video per hour. 16 Mbps × 3,600 ÷ 8 ÷ 1,000 = 7.2 GB per hour.
- Video per day. 3.5 h × 7.2 GB = 25.2 GB.
- Audio per hour. 160 kbps is 0.16 Mbps, so 0.16 × 0.45 = 0.072 GB per hour.
- Audio per day. 2 h × 0.072 = 0.144 GB.
- Streaming per day. 25.2 + 0.144 = 25.344 GB.
- Streaming per month. 25.344 × 30.44 = 771.47 GB.
- Total per month. 771.47 + 50 = 821.47 GB, which is 821.47 ÷ 1,229 = 66.8% of the cap. No overage.
- Headroom for video. Audio costs 0.144 × 30.44 = 4.38 GB a month, so audio plus other traffic is 54.38 GB. That leaves 1,229 − 54.38 = 1,174.62 GB for video, which at 7.2 GB per hour buys 163.1 hours of 4K a month, or about 5.4 hours a day.
- Highest bitrate that fits. At the current 3.5 hours a day the video allowance is 1,174.62 GB spread over 3.5 × 30.44 = 106.54 hours, so 1,174.62 ÷ 106.54 = 11.02 GB per hour, and 11.02 ÷ 0.45 = 24.5 Mbps.
Now change one thing: a second 4K stream running through the same 3.5 hours. Video per day doubles to 50.4 GB, the month becomes 50.544 × 30.44 + 50 = 1,588.6 GB, and you are 359.6 GB past the cap — eight 50 GB blocks at $10, so $80. That single input is the difference between a comfortable plan and an expensive one.
How to read the result
Treat 85% of the cap as the line where you should act — that is where this calculator turns the cap figure amber, and it is a working rule rather than a published threshold. Household usage is not steady: one game release, one visiting relative, one weekend of continuous television, and an average month sitting at 85% becomes a month that breaches. Below 60% you have real room to raise quality or add a screen.
The video hours the cap allows figure is the one to compare against reality. Divide it by 30.44 to get hours a day, and hold it next to what your household actually watches. If the answer is 3 hours a day and your teenagers watch 5, the quality setting is the variable to change, not the viewing.
The highest bitrate that fits the cap tells you which tier to select. If it comes out at 24.5 Mbps you can stay on 4K with room to spare; at 4 Mbps you belong on 720p; below 1.5 Mbps the plan cannot support serious video streaming and the fix is a different plan, not a different setting. Dropping from 4K to 1080p cuts data by roughly two thirds — 7.2 GB per hour to 2.25 at the tier bitrates used on this page — and whether you can see what you gave up depends on your screen size and seating distance, because 4K detail only resolves inside a certain distance of the screen. The TV size and viewing distance calculator gives that distance for your set; if you sit further back than it, you are paying the 4K data bill for detail your eye cannot resolve.
Finally, read the overage figure as a monthly recurring cost, not a one-off. Providers bill overage in whole blocks, so an overshoot of 3 GB and an overshoot of 49 GB cost exactly the same. If you are consistently paying two or more blocks, the unlimited add-on is usually the cheaper line item — compare it directly against the charge shown here.
Data cost of each quality tier
| Quality | Typical bitrate | GB per hour | Hours per 100 GB | Hours in a 1,229 GB cap |
|---|---|---|---|---|
| Data saver / low | 0.7 Mbps | 0.32 | 317 | 3,902 |
| SD 480p | 1.5 Mbps | 0.68 | 148 | 1,821 |
| HD 720p | 3 Mbps | 1.35 | 74 | 910 |
| Full HD 1080p | 5 Mbps | 2.25 | 44 | 546 |
| 4K UHD | 16 Mbps | 7.20 | 14 | 171 |
| 4K high bitrate / live sport | 25 Mbps | 11.25 | 9 | 109 |
| Music, normal | 160 kbps | 0.072 | 1,389 | 17,069 |
| Music, lossless | 1,411 kbps | 0.635 | 158 | 1,936 |
Bitrates are representative sustained averages for each tier, not guarantees; individual services vary by title, codec and device. Use your player's diagnostics overlay for your own figure and enter it as a custom bitrate.
GB and GiB are not the same unit
Your provider's usage meter counts decimal gigabytes: 1 GB = 1,000,000,000 bytes. Windows and many routers report the 1,024-based unit, which IEC 80000-13 names the gibibyte (GiB) and which is 7.4% larger. A 1,024 GiB figure on your router is 1,100 GB on your bill. This calculator works in decimal GB throughout, because that is what caps and overage charges are written in; enter a router figure using the GiB unit selector and it converts for you.
Mistakes that make a data estimate wrong
- Confusing bits with bytes. A 25 Mbps stream is 3.125 MB per second, not 25. Getting this wrong overstates or understates your total by a factor of eight.
- Using peak bitrate instead of sustained. Encoders spike on high-motion scenes and idle on static ones. The average across an episode is what you pay for.
- Forgetting simultaneous streams. Four screens on one plan is four times the data for the same hours on the clock. This is the single biggest driver in a family household.
- Counting only video. A single current-generation console game download can outweigh a week of 4K viewing, system updates land without warning, and continuous cloud photo backup runs quietly all month. Sizes vary far too much by title and platform to estimate, so read last month's total from your provider's usage meter and enter it as one lump.
- Assuming a downloaded show is free. Downloading for offline viewing costs the same data as streaming it once, and streaming it again afterwards costs it again.
Bandwidth, data caps and when to use a different tool
Bandwidth and data volume are different constraints, and confusing them wastes money. Bandwidth is the rate your connection can sustain at any instant, and it decides whether a stream plays without buffering: four simultaneous 4K streams need roughly 64 Mbps of headroom regardless of your monthly allowance. The FCC's broadband speed guidance sets out the per-activity rates that matter for that question. Data volume is the monthly total, and it decides your bill. A 1 Gbps connection with a 1.2 TB cap gives you flawless playback and an overage charge in the same month.
If your question is how long a fixed download takes rather than how much a habit consumes over a month, use the data transfer time calculator, which works the same bits-to-bytes conversion in the time direction. If you are pricing an outage or a service credit against a promised availability figure, the uptime SLA downtime calculator converts a percentage into real minutes. And once you know what your streaming actually costs in data, the next question is usually what it costs in money: the subscription cost audit calculator totals every recurring service and prices each one per hour you actually use it.
Two things this calculator deliberately does not model. It does not account for protocol overhead — TCP/IP headers, retransmissions and adaptive-bitrate probing add a few percent on top of the media payload, which is inside the noise created by your bitrate estimate. And it assumes your quality setting is the one that actually gets delivered; adaptive streaming will silently drop you to a lower tier on a congested connection, which means your real usage may come in under this estimate. Both errors are small relative to guessing the wrong number of simultaneous streams.
Key terms
- Bitrate
- The number of bits per second a stream delivers. Quoted in Mbps for video and kbps for audio. Sustained bitrate, not peak, is what determines data use.
- Data cap
- A monthly volume allowance in a broadband plan. Passing it triggers either an overage charge in fixed blocks or a speed reduction for the rest of the cycle.
- Adaptive bitrate
- The technique by which a player switches quality mid-stream to match available bandwidth. It means your delivered quality — and therefore your data use — can be lower than the tier you selected.