UTF-8/UTF-16 Byte Calculator
Compare UTF-8 and UTF-16 byte size with optional BOM handling, then inspect chart, summary table, and per-character detail rows to diagnose encoding cost differences quickly.
UTF-8/UTF-16 Byte Calculator
Compare UTF-8 and UTF-16 byte sizes instantly, then inspect per-character details to see exactly where byte usage grows.
UTF-8 vs UTF-16 Byte Comparison (Bar Chart)
The chart updates after calculation. The same values are also available in the tables below.
Encoding Summary Table
| Item | Bytes | Note |
|---|---|---|
| Run a calculation to display UTF-8/UTF-16 summary values. | ||
Per-Character Detail Table
| # | Char | Code Point | UTF-8 | UTF-16 | UTF-16 Position | Note |
|---|---|---|---|---|---|---|
| Run a calculation to display character-level analysis. | ||||||
All calculations run in your browser. Your input text is not sent to the server.
What is the UTF-8/UTF-16 Byte Calculator?
The UTF-8/UTF-16 Byte Calculator helps you compare the byte footprint of the same text across encodings. This is useful when API limits, DB fields, or message systems are defined by byte length rather than character count.
Instead of showing only total bytes, it also provides character-level detail so you can quickly identify where emojis, non-Latin text, or symbols increase size.
When to use it
- Validating strings against byte-based API/DB limits
- Estimating payload size for multilingual messages with emoji
- Comparing UTF-8 vs UTF-16 for storage/transmission decisions
- Checking file size impact when BOM is included
- Debugging byte spikes at character level
Key Features
- Summary cards: character count, code units, UTF-8/UTF-16 totals, and difference
- Bar chart: quick visual comparison of UTF-8 vs UTF-16 totals
- Summary table: compare BOM-off and BOM-on totals
- Detail table: code point, UTF-8/UTF-16 bytes, and UTF-16 position per character
- Copy result: export key metrics as plain text for docs/tickets
How to use
- Enter or paste the text you want to analyze.
- Enable BOM options if your target output includes BOM.
- Click Calculate to update cards, chart, and tables.
- Use the detail table to identify heavy characters.
- Use Copy Result to share metrics quickly.
Calculation rules
- UTF-8: 1โ4 bytes per character (ASCII 1, emoji 4)
- UTF-16: 2 bytes per code unit; supplementary chars use 4 bytes (surrogate pair)
- BOM: UTF-8 adds +3 bytes, UTF-16 adds +2 bytes (optional)
If the chart cannot load, the same values remain available in text/table fallback so interpretation is unaffected.
Frequently Asked Questions
Why are UTF-8 and UTF-16 byte sizes different?
They encode characters differently. ASCII-heavy text often favors UTF-8, while some character mixes may make UTF-16 similar or smaller.
Why can character count differ from UTF-16 code unit count?
Supplementary characters (such as many emojis) require two UTF-16 code units. So code units can be larger than character count.
When should I enable BOM options?
Enable BOM only if your real output file/text includes BOM. For most API/DB string checks, BOM is usually disabled.
Is my input sent to a server?
No. Everything is processed locally in your browser.
Do UTF-16LE and UTF-16BE have different total byte size?
For the same text, total byte size is the same. LE/BE changes byte order (endianness), not the overall character data length.