Tinker Tools

File Size Calculator Instantly

Convert between file size units: bytes, KB, MB, GB, TB, and PB. Toggle between decimal (SI) and binary (IEC) standards with precision control.

CalculatorDecimal (SI) mode
Conversion Results
BytesB
1000000.00
KilobytesKB
1000.00
MegabytesMB
1.00
GigabytesGB
0.00
TerabytesTB
0.00
PetabytesPB
1.00e-9

Quick Reference

1 KB1,000 B1 MB1,000,000 B1 GB1,000,000,000 B1 TB1,000,000,000,000 B

How it works

1. Enter Value

Type a number and select the source unit (B, KB, MB, GB, TB, or PB). The conversion updates instantly as you type.

Real-time

2. Toggle Standard

Switch between decimal (SI: 1 KB = 1,000 B) and binary (IEC: 1 KiB = 1,024 B) standards to see how values differ across systems.

SI vs IEC

3. Copy Results

See all conversions at a glance with adjustable precision. Copy any value to your clipboard with a single click.

One-click Copy

What is File Size Calculation?

File size calculation is the process of converting between different units of digital storage measurement — bytes, kilobytes, megabytes, gigabytes, terabytes, and beyond. This sounds trivial until you realize there are two competing systems for these units, and the industry uses them inconsistently. A kilobyte is either 1,000 bytes (decimal, SI standard) or 1,024 bytes (binary, traditional computing convention). The difference is small at the kilobyte level — just 2.4% — but it compounds at every step. A terabyte is either 1,000,000,000,000 bytes (decimal) or 1,099,511,627,776 bytes (binary). That is a 10% gap. When you buy a 1 TB hard drive and your operating system reports 931 GB, this is exactly why.

The IEC 80000-13 standard attempted to resolve this confusion by introducing distinct unit names. Binary units use a "bi" infix: kibibyte (KiB) for 1,024 bytes, mebibyte (MiB) for 1,048,576 bytes, gibibyte (GiB) for 1,073,741,824 bytes, and tebibyte (TiB) for 1,099,511,627,776 bytes. Decimal units keep the familiar names: kilobyte (KB) for 1,000 bytes, megabyte (MB) for 1,000,000 bytes, gigabyte (GB) for 1,000,000,000 bytes. In practice, adoption has been mixed. Linux and macOS use decimal units in their file managers. Windows uses binary values but labels them with decimal unit names — calling 1,073,741,824 bytes "1 GB" when it is technically 1 GiB. Storage manufacturers use decimal units because the numbers are larger. RAM manufacturers use binary units because memory addresses are powers of two. A file size calculator cuts through this mess and gives you the exact number in whatever unit system you need.

Beyond simple unit conversion, file size calculation matters for practical engineering decisions. API payload limits, email attachment caps, CDN bandwidth quotas, database column sizes, upload form restrictions, and mobile app bundle budgets are all defined in specific units. Knowing that your 4.7 MB JSON response is 4,700,000 bytes (decimal) versus 4,922,982 bytes if someone meant 4.7 MiB (binary) can be the difference between hitting a limit and staying under it. Network transfer rates add another layer of complexity because they are measured in bits per second — not bytes. Downloading a file at 100 Mbps means 100 megabits per second, which is 12.5 megabytes per second, which is about 11.92 mebibytes per second. A calculator that handles all these conversions prevents the mental arithmetic errors that lead to misconfigured limits and unexpected failures.

Key Features and Benefits

  • Binary and Decimal Unit Conversion — Convert between binary units (KiB, MiB, GiB, TiB, PiB) and decimal units (KB, MB, GB, TB, PB) with full precision. Enter a value in any unit and see the equivalent in every other unit simultaneously. The calculator uses exact arithmetic — not floating-point approximations — so you get precise results even for very large or very small values. This is essential when you need to specify exact byte counts for configuration files, API headers, or storage allocation.
  • Bit and Byte Conversion — Switch between bits and bytes with a single toggle. One byte equals 8 bits — always, regardless of the unit prefix. But confusing bits and bytes is one of the most common mistakes in computing. Internet speeds are quoted in megabits per second (Mbps) while file sizes are quoted in megabytes (MB). A 100 Mbps connection downloads at 12.5 MB per second, not 100 MB per second. The calculator makes this conversion explicit so you can accurately estimate download times and bandwidth requirements.
  • Transfer Time Estimation — Enter a file size and a transfer speed and get the estimated transfer time. Upload a 2 GB file over a 10 Mbps connection? That is about 26 minutes and 40 seconds — assuming the full bandwidth is available and there is no protocol overhead. The calculator accounts for the bit-versus-byte distinction automatically. It also shows you what speed you would need to transfer a given file in a target time, which is useful for setting SLA expectations and infrastructure planning.
  • Common File Size References — The calculator includes reference sizes for common file types: a typical JPEG photo (2-5 MB), a raw camera image (25-60 MB), a minute of MP3 audio at 320 kbps (2.4 MB), a minute of 1080p H.264 video (150-300 MB), a minute of 4K H.265 video (375-750 MB), a typical web page (2-3 MB), a React production bundle (200-500 KB). These references help you sanity-check your calculations and make quick estimates without looking up file sizes every time.
  • Storage Planning Calculations — Calculate how many files of a given size fit on a storage device, or how much storage you need for a given number of files. Planning a video surveillance system with 20 cameras recording 1080p at 4 Mbps continuously? That is about 42 GB per camera per day, or 840 GB per day for all cameras, or roughly 25 TB per month. The calculator does this arithmetic in seconds, accounting for the binary-decimal distinction that can throw off your estimate by 7-10% at the terabyte level.
  • Precision Control — Choose how many decimal places to display in the output. For quick estimates, 2 decimal places are enough. For exact specifications in technical documents or configuration files, you might need 6 or more. The calculator also shows the exact byte count for any input, which is the only truly unambiguous way to specify a file size. When a specification says the maximum upload size is 10 MB, knowing whether that means 10,000,000 or 10,485,760 bytes matters — and the exact byte count removes all doubt.

How to Calculate and Convert File Sizes

  1. 1

    Enter Your Known Value

    Type the file size you want to convert into the input field and select its unit from the dropdown. If you have a byte count — like 157,286,400 — enter it directly. If you have a human-readable size like 150 MB, enter 150 and select MB (decimal) or MiB (binary) depending on the source. If the source is ambiguous — and it often is — check how the source system defines its units. AWS S3 uses binary units. Apple uses decimal units in macOS. Windows uses binary values with decimal labels. Knowing the source convention is half the battle.

  2. 2

    Review All Unit Conversions

    The calculator displays the equivalent value in every common unit: bytes, KB, KiB, MB, MiB, GB, GiB, TB, TiB, and their bit equivalents. Scan through the results to find the unit you need. For a 157,286,400-byte file, you will see: 157.29 MB (decimal), 150.00 MiB (binary), 1,258.29 Mb (megabits), 1,200.00 Mib (mebibits). These are all different numbers describing the same amount of data. The right one depends on your context.

  3. 3

    Estimate Transfer Times

    If you need to know how long a file will take to upload or download, enter your connection speed. A typical home broadband connection is 100-300 Mbps download and 10-30 Mbps upload. Corporate networks might offer 1 Gbps. Mobile 4G connections average 20-50 Mbps in good conditions. 5G varies wildly from 50 Mbps to 1 Gbps depending on the band and distance from the tower. Enter your effective speed and the calculator shows the transfer time. Remember that real-world speeds are typically 60-80% of the advertised maximum due to protocol overhead, network congestion, and distance from the server.

  4. 4

    Plan Storage Requirements

    For capacity planning, use the calculator's batch mode. Enter the average file size, the number of files, and any growth projections. If you are archiving 10,000 documents averaging 2.5 MB each, you need 25 GB — but add a 20% buffer for metadata, file system overhead, and growth. If you are planning a media server with 500 hours of 1080p video at an average bitrate of 8 Mbps, that is roughly 1.8 TB. The calculator handles the unit conversions and multiplication, so you can focus on the architecture decisions rather than the arithmetic.

  5. 5

    Export or Copy Results

    Copy the conversion results for use in documentation, configuration files, or team communications. The calculator provides values in multiple formats: plain numbers, formatted with thousand separators, and scientific notation for very large values. For configuration files that expect specific units — like Nginx's client_max_body_size directive (which accepts values like 10m for 10 mebibytes) or Kubernetes resource limits (which use Mi, Gi suffixes for binary units) — the calculator shows the exact value in the expected format.

Expert Tips for File Size Calculations

Always specify the unit system when communicating file sizes in technical documents. Writing "the maximum upload size is 50 MB" is ambiguous. Does that mean 50,000,000 bytes or 52,428,800 bytes? The difference is nearly 2.5 million bytes — enough to cause real problems at the boundary. Instead, write "the maximum upload size is 50 MB (50,000,000 bytes)" or "50 MiB (52,428,800 bytes)." Including the exact byte count eliminates all ambiguity. This is especially important in API documentation, infrastructure specifications, and SLA agreements where the precise limit determines whether a request succeeds or fails.

Understand file system overhead when planning storage. The formatted capacity of a disk is always less than the raw capacity because of partition tables, file system metadata, journaling, and block allocation. A 1 TB SSD formatted with ext4 provides about 916 GiB of usable space after formatting. NTFS and APFS have similar overhead. Then there is block-level waste: if your file system uses 4 KiB blocks — the default on most systems — a 1-byte file still consumes 4 KiB of disk space. A directory with a million tiny files can waste gigabytes on block padding alone. This matters for applications that create many small files, like caches, email stores, and version control repositories. When your storage math does not add up, block waste and file system overhead are usually the explanation.

Network speed calculations require careful attention to units and overhead. ISPs advertise speeds in megabits per second, but actual file transfer rates are lower for multiple reasons. TCP/IP headers add overhead — roughly 3-5% for typical packet sizes. TLS encryption adds another small overhead. Application-layer protocols like HTTP add their own headers. And the advertised speed is the physical layer maximum, not the throughput you achieve at the application layer. A connection advertised at 1 Gbps delivers maybe 900-940 Mbps of actual data throughput under ideal conditions. For planning purposes, estimate 75-80% of the advertised speed for LAN transfers and 50-70% for WAN transfers across the internet, depending on distance and congestion.

Use file size awareness to make better engineering decisions. A React production bundle of 500 KB takes about 1.5 seconds to download on a 3G mobile connection — which is still common in much of the world. Every additional 100 KB adds roughly 0.3 seconds on 3G. That is why performance budgets exist. Similarly, a JSON API response of 2 MB might be fine on a backend-to-backend call over a fast network, but sending that to a mobile client on a metered connection wastes bandwidth and battery. Knowing the exact size of your payloads, bundles, images, and data transfers — and what those sizes mean in terms of real-world performance — is the foundation of good performance engineering. The calculator is the starting point, but the habit of thinking in bytes is what makes the difference.

Related Tools

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CSV to JSON

Compare data format sizes for storage decisions

File size calculation supports every other tool in your workflow by giving you the numbers you need to make informed decisions. After calculating your target image size, the image compressor reduces your files to hit that target. Formatting JSON and checking its size tells you whether your API response fits within payload limits. Converting between CSV and JSON and comparing the resulting file sizes helps you choose the most efficient format for storage and transfer. The calculator is the measuring tape — the other tools are what you use once you know the measurements.

Frequently Asked Questions

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