Check payload size before sending API requests with byte-limit headers.
Byte size counter
Paste any text to see its exact byte size in UTF-8 encoding — useful for payloads, headers, storage limits, and API constraints.
51Bytes (UTF-8)
0.0498 KBKilobytes
0 MBMegabytes
51Characters
0Extra bytes (multi-byte chars)
UTF-8Encoding
Byte Size Counter
About this tool
Free online byte size calculator — paste text to instantly see its exact size in bytes, KB, and MB using UTF-8 encoding.
No signup requiredRuns in your browserInstant results
Verify that a message or token fits within storage or transmission constraints.
Understand how multi-byte Unicode characters affect the actual byte length of a string.
Why use this tool?Key benefits
Works instantly
Paste your input and get the result immediately — no page reload, no waiting, no configuration needed to get started.
Your data stays private
All Byte Size Counter processing runs locally in your browser. Nothing you paste is sent to a server or stored anywhere.
Focused workspace
A dedicated page for Byte Size Counter means a clean, distraction-free workspace you can bookmark and come back to anytime.
Frequently asked questionsCommon questions answered
These answers explain common byte size counter tasks, expected input formats, and edge cases so both visitors and search engines can understand what this tool does.
Why does character count differ from byte count?
In UTF-8 encoding, characters outside the basic ASCII range (such as emoji or accented letters) use multiple bytes. A single emoji can be 3 or 4 bytes, so byte count is always equal to or greater than character count.
What encoding does this tool use?
This tool measures byte size using UTF-8 encoding, which is the standard for the web and most modern APIs and databases.
Why would I need to know the byte size of a string?
Many systems enforce byte-based limits rather than character limits — including HTTP headers, message queues, database columns, and JWT token size restrictions.