Methodology
Every number on SavingBits is computed at build time from a small set of definitions and published figures. Here is all of it.
Units
Decimal (SI) prefixes: 1 KB = 1,000 bytes, 1 MB = 10⁶, 1 GB = 10⁹, 1 TB = 10¹². Binary (IEC 80000-13): 1 KiB = 1,024 bytes, 1 MiB = 2²⁰, 1 GiB = 2³⁰, 1 TiB = 2⁴⁰. Capacities are taken as decimal, the way drives, cards, phones and data plans are sold. The GB / GiB switch in the header re-expresses sizes in binary units; it never changes the underlying bytes. Speeds are bits per second: 1 Mbps = 1,000,000 bits per second.
Transfer time
time = bytes × 8 ÷ (bits per second × efficiency). We publish three efficiencies. None (100 %) is the theoretical floor. TCP/IP (94.9 %, computed): a full 1,500-byte Ethernet packet carries 1,460 bytes of TCP payload and occupies 1,538 bytes of line time (14-byte header, 4-byte checksum, 8-byte preamble, 12-byte inter-frame gap). Typical (80 %) is our estimate for Wi-Fi, busy servers and shared lines. It is not a measurement of any particular connection.
Media sizes
Audio and video sizes are bitrate × duration ÷ 8. Songs are assumed to last 3.5 minutes (estimate). Photo and document sizes are typical values unless a maker publishes one. Each figure carries one of three labels:
- published: the maker's or service's own figure, restated in our words, with the date we checked it.
- computed: arithmetic from a published bitrate or speed (for example YouTube's recommended speeds → GB per hour, which gives a ceiling, not typical use).
- estimate: our own typical value. Real files vary, and the page says so.
| Item | Size | Basis | Note or source |
|---|---|---|---|
| Phone photo, 12 MP HEIF/HEIC | 2 MB | estimate | Modern iPhones save HEIF by default. 12 MP HEIF files are commonly 1.5–2.5 MB; detailed or night scenes run larger. |
| Phone photo, 12 MP JPEG | 3.5 MB | estimate | Most Android phones and 'Most compatible' iPhones save JPEG, roughly 3–5 MB at 12 MP. |
| Camera photo, 24 MP JPEG (fine) | 10 MB | estimate | A 24-megapixel mirrorless or DSLR camera at its finest JPEG setting; typically 8–14 MB. |
| Camera RAW, 24 MP | 30 MB | estimate | Lossless-compressed RAW from a 24 MP sensor is commonly 25–35 MB; uncompressed RAW is about 48 MB. |
| Apple ProRAW, 12 MP | 25 MB | published | Apple Support, 'About Apple ProRAW' (article 119916): about 25 MB per 12 MP ProRAW photo |
| Apple ProRAW, 48 MP | 75 MB | published | Apple Support, 'About Apple ProRAW' (article 119916): about 75 MB per 48 MP ProRAW photo |
| MP3 at 128 kbps | 3.36 MB | computed | The classic 'small' MP3 setting. |
| AAC at 256 kbps (iTunes / Apple Music standard) | 6.72 MB | computed | Apple sells and streams its standard-quality music as 256 kbps AAC. |
| MP3 / Ogg at 320 kbps | 8.4 MB | computed | The highest MP3 bitrate; also Spotify's 'Very high' setting. |
| CD-quality FLAC (16-bit / 44.1 kHz) | 23.6 MB | estimate | Uncompressed CD audio is exactly 1,411.2 kbps; FLAC typically shrinks it to 50–70 % depending on the music. We use 900 kbps. |
| Hi-res FLAC (24-bit / 96 kHz) | 76.1 MB | estimate | Uncompressed 24/96 stereo is exactly 4,608 kbps; FLAC typically lands near 2,500–3,300 kbps. |
| 720p, 30 fps (H.264, 5 Mbps) | 2.25 GB per hour | published | YouTube Help, 'Recommended upload encoding settings': 5 Mbps for 720p at 24–30 fps |
| 1080p, 30 fps (H.264, 8 Mbps) | 3.6 GB per hour | published | YouTube Help, 'Recommended upload encoding settings': 8 Mbps for 1080p at 24–30 fps |
| 1080p, 60 fps (H.264, 12 Mbps) | 5.4 GB per hour | published | YouTube Help, 'Recommended upload encoding settings': 12 Mbps for 1080p at 48–60 fps |
| 1440p, 30 fps (H.264, 16 Mbps) | 7.2 GB per hour | published | YouTube Help, 'Recommended upload encoding settings': 16 Mbps for 1440p at 24–30 fps |
| 4K, 30 fps (H.264, 40 Mbps) | 18 GB per hour | published | YouTube Help, 'Recommended upload encoding settings': 35–45 Mbps for 2160p at 24–30 fps (we use the middle, 40) |
| 4K, 60 fps (H.264, 60 Mbps) | 27 GB per hour | published | YouTube Help, 'Recommended upload encoding settings': 53–68 Mbps for 2160p at 48–60 fps (we use 60) |
| iPhone 1080p, 30 fps (HEVC) | 3.6 GB per hour | estimate | The per-minute size iPhone shows under Settings › Camera › Record Video (as widely reported; check your own phone). |
| iPhone 4K, 30 fps (HEVC) | 10.2 GB per hour | estimate | The per-minute size iPhone shows under Settings › Camera › Record Video (as widely reported; check your own phone). |
| iPhone 4K, 60 fps (HEVC) | 24 GB per hour | estimate | The per-minute size iPhone shows under Settings › Camera › Record Video (as widely reported; check your own phone). |
| Word / Docs file, text only | 100 KB | estimate | A few pages of text with light formatting: tens to a few hundred KB. |
| PDF report with some images | 1 MB | estimate | Text PDFs are often under 0.5 MB; image-heavy ones run to tens of MB. |
| E-book (EPUB), novel | 2 MB | estimate | A novel's text is under 1 MB; the cover and fonts usually bring an EPUB to 1–3 MB. |
HEVC and AV1 typically need about 40–50 % less bitrate than H.264 for similar quality. These factors are rules of thumb (estimates); real savings depend on the encoder and the footage.
Streaming figures
Checked 2026-10-25 against each service's own help pages:
- Netflix published: Netflix Help Center, 'How to control how much data Netflix uses' (help.netflix.com/en/node/87). Netflix publishes these as 'up to' figures per device. Real use is often lower, since Netflix adapts to the connection and the title.
- YouTube computed: YouTube Help, 'Video resolution & internet speed' (support.google.com/youtube/answer/78358): recommended sustained speeds. YouTube publishes the connection speed it recommends, not data per hour. We convert that speed to GB per hour, so these are ceilings; YouTube's real bitrates are usually lower, especially with AV1 or VP9.
- Spotify computed: Spotify Support, 'Audio quality' (support.spotify.com): approximate bitrates per quality setting. Spotify publishes the bitrate of each setting; we turn it into data per hour. Lossless (up to 24-bit/44.1 kHz FLAC) has no published bitrate; its ceiling is uncompressed PCM at 2,116.8 kbps, about 0.95 GB per hour, and FLAC comes in below that.
- Apple Music computed: Apple: standard-quality Apple Music streams are 256 kbps AAC. Standard quality only. Lossless and Hi-Res Lossless use several times more.
- Zoom computed: Zoom Support, 'Zoom system requirements: Windows, macOS, Linux' (support.zoom.com, KB0060748): bandwidth requirements. Zoom publishes the bandwidth it needs in each direction; we add upload and download, because both count towards a data cap. Treat these as ceilings.
Validation: 15 of 15 checks pass
On every build, the site's own functions recompute these values and the build stops if any of them drifts from the independently known figure. The browser calculators use a JavaScript port of the same functions; a separate check compares the two on 681 cases (unit formatting, durations, transfer times), and all of them agreed when it last ran.
| Case | Computed | Known value | Source of the known value | Result |
|---|---|---|---|---|
| 1 TB in GiB (why a 1 TB drive shows 931 GB) | 931.32 GiB | 931.32 GiB | SI and IEC 80000-13 prefix definitions; the figure Windows shows for a 1 TB drive | ✓ pass |
| 2 TB in TiB (shown as 1.81 TB) | 1.819 TiB | 1.819 TiB | IEC binary prefixes; Windows truncates it to 1.81 TB | ✓ pass |
| 256 GB in GiB | 238.42 GiB | 238.42 GiB | The '238 GB' Windows shows for a 256 GB SSD | ✓ pass |
| Bytes in 1 GiB | 1,073,741,824 bytes | 1,073,741,824 bytes | 2³⁰, IEC 80000-13 | ✓ pass |
| 4.7 GB DVD in GiB | 4.377 GiB | 4.377 GiB | The DVD-5's 4.7 billion bytes, widely quoted as 4.37 GiB | ✓ pass |
| 1.44 MB floppy in bytes (1,440 KiB) | 1,474,560 bytes | 1,474,560 bytes | The 3½-inch HD floppy: 2 sides × 80 tracks × 18 sectors × 512 bytes | ✓ pass |
| 1 GB at 100 Mbps, no overhead | 80 s | 80 s | 8,000 megabits ÷ 100 megabits per second | ✓ pass |
| 1 Gbps in megabytes per second | 125 MB/s | 125 MB/s | Gigabit Ethernet's 125 MB/s line rate | ✓ pass |
| TCP payload efficiency, 1500-byte MTU Ethernet | 0.9493 | 0.949 | Widely published 94.9 % maximum TCP goodput on Ethernet (1,460 / 1,538 bytes) | ✓ pass |
| 320 kbps MP3, one minute | 2.4 MB | 2.4 MB | The usual '2.4 MB per minute' for 320 kbps MP3 | ✓ pass |
| CD audio bitrate (44.1 kHz × 16 bit × 2 channels) | 1,411.2 kbps | 1,411.2 kbps | Red Book CD-DA: 1,411.2 kbps | ✓ pass |
| 74-minute audio CD, PCM bytes | 783,216,000 bytes | 783,216,000 bytes | Red Book: 74 min × 60 × 75 sectors × 2,352 bytes = 783,216,000 | ✓ pass |
| Netflix 4K: 15 Mbps (its recommended speed) for an hour | 6.75 GB | 7 GB | Netflix's own published figures: 15 Mbps recommended for Ultra HD and 'up to 7 GB per hour' (6.75 GB computed) | ✓ pass |
| Spotify Very high (320 kbps) for an hour | 144 MB | 144 MB | 320 kbps × 3,600 s ÷ 8; the commonly quoted ~144 MB per hour | ✓ pass |
| 12 MP image as uncompressed 24-bit bitmap | 36 MB | 36 MB | 3 bytes per pixel × 12 million pixels | ✓ pass |
What we do not do
We don't measure your connection or read your device. The calculators run entirely in your browser and send nothing anywhere. We don't copy text from the services' help pages; we restate their figures and link to the source by name. When we're unsure of a figure we label it an estimate rather than guess.
Licences
Unit definitions are international standards (SI, IEC 80000-13). The service figures are facts restated with attribution. All text, code and illustrations on this site are original. The site uses no third-party images, fonts or scripts.