Byte Calculator

Convert data sizes in binary (1024) and SI (1000) modes. Calculate transfer time at any speed.

Last reviewed: June 2026
Reviewed by , software engineer ยท last updated June 2026

New to this tool? Click here for instructions

Enter any data size to convert all units instantly.

Transfer Time Calculator

Enter a file size above and a connection speed to calculate transfer time.

Binary Reference Table (powers of 1024)

UnitSymbolBytes (exact)Power

How to Use the Byte Calculator

Choose Binary mode when you want the 1024-based numbers common in operating systems and developer tooling. Choose SI / Decimal mode when you want the 1000-based numbers printed on storage devices, network hardware, and product sheets.

  1. Pick Binary (1024) or SI / Decimal (1000).
  2. Type a value in any unit row, such as Bytes, KB, MB, GB, TB, or PB.
  3. Read the converted values immediately in the other rows.
  4. Optionally enter a connection speed to estimate transfer time for the current file size.

When to Use the Tool in Real Workflows

Use this calculator when you are sizing upload limits, checking object-storage quotas, comparing drive labels with operating-system file sizes, estimating backup windows, or explaining why a "1 TB" disk can appear near 931 GiB in some tools.

How It Works

All conversion math runs in local JavaScript. The page multiplies your entered value by the selected unit factor, then divides by each target unit factor. The transfer-time panel converts the selected network speed to bytes per second and divides the current byte total by that rate. No file-size value is sent to a backend service.

The binary side follows 1024-based powers used for KiB, MiB, GiB, and related units. The decimal side follows SI powers of 1000. For standards background, see NIST's binary prefix reference and SI prefix guidance.

Tips, Edge Cases, or Limitations

  • The visible labels use familiar KB/MB/GB names, so check the active Binary or SI chip before copying a result.
  • Network speeds written as Mbps or Gbps are bits per second; transfer sizes are bytes, so the calculator divides bit rates by 8.
  • Transfer estimates assume ideal throughput. Protocol overhead, throttling, Wi-Fi quality, and provider limits can make real transfers slower.
  • Very large values may display in scientific notation to keep the fields readable.

Frequently Asked Questions

KB (kilobyte) in SI mode = 1,000 bytes. KiB (kibibyte) in binary mode = 1,024 bytes. Hard drive manufacturers use SI (1 TB = 1,000,000,000,000 bytes), while operating systems traditionally use binary units (1 GB = 1,073,741,824 bytes).
To calculate file transfer time, enter the file size and your connection speed in the Byte Calculator. The tool will automatically calculate the estimated transfer time based on the provided values.
This discrepancy arises because Windows uses binary units (1 GiB = 1,073,741,824 bytes) while hard drive manufacturers use SI units (1 TB = 1,000,000,000,000 bytes). A 1 TB drive appears as about 931 GiB in Windows Explorer.
In SI decimal units, 1 petabyte (PB) is 1,000 terabytes or 1,000,000,000,000,000 bytes. In binary units, 1 pebibyte (PiB) is 1,024 tebibytes, or 1,125,899,906,842,624 bytes.
In SI mode, 1 gigabyte (GB) is 1,000,000,000 bytes. In binary mode, the tool treats the GB field as 1,073,741,824 bytes for operating-system-style calculations.

Example walk-through

Convert 1.5 GiB to bytes and estimate transfer time

Step 1. Leave the calculator in Binary mode.

Step 2. Click Try Example. The tool enters 1.5 in the Gigabytes row and fills the related rows.

1.5 GB x 1,073,741,824 bytes = 1,610,612,736 bytes

Step 3. Enter 100 in Connection speed and keep Mbps selected.

Step 4. The transfer panel estimates the time by dividing 1,610,612,736 bytes by 12,500,000 bytes per second.

about 2m 9s at 100 Mbps, before overhead