Editorial principles
- Every formula and figure is verified against official sources (laws and public agency notices).
- When rates change, the calculator and its guide content are updated together.
- Reported errors are fixed as soon as they are confirmed.
Calculators by Sin Dongho (178)
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Education
TOEIC Score Converter
Free TOEIC Listening & Reading score converter. Combine LC and RC sub-scores into total (10–990) and see your ETS proficiency band — used by employers in 160+ countries.
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Real Estate
Real Estate Agent Commission Calculator
Free real estate commission calculator updated for the 2024 NAR settlement. Compute total seller commission, listing agent share, and buyer agent share by sale price.
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Real Estate
Real Estate Transfer Tax Calculator
Free real estate transfer tax calculator. Estimate state and county transfer/deed taxes by state — DE 4%, NY 0.4-2.625%, CT 1.25%+, others. 13 states have no transfer tax.
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Education
GPA Calculator
Free GPA calculator using the US 4.0 scale. Enter course grades and credit hours to compute your unweighted grade point average for college admission, transfer, and scholarship applications.
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Education
Standard Deviation Calculator
Free standard deviation calculator. Compute population SD, sample SD (Bessel-corrected), variance, mean, min, max from any list of numbers — for statistics, finance, and data analysis.
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Developer Tools
Number Base Converter
Free online number base converter. Convert between binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16). Includes byte split and color hex preview.
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Developer Tools
JSON Formatter
Free online JSON formatter, validator, and minifier. Pretty-print compact JSON with proper indentation, validate against RFC 8259 syntax, and minify back to a single line.
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Developer Tools
Base64 Encoder / Decoder
Free Base64 encoder and decoder following IETF RFC 4648. Encode strings or files to Base64; decode Base64 back to text. Standard and URL-safe variants supported.
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Developer Tools
Color Converter
Free color converter between HEX, RGB, HSL, HSV, and OKLCH. Pick a color or paste any format and see all CSS-compatible representations side by side with WCAG contrast.
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Developer Tools
URL Encoder / Decoder
Free URL encoder and decoder following IETF RFC 3986. Encode special characters for query strings, decode percent-encoded URLs, and choose between encodeURI and encodeURIComponent.
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Developer Tools
JWT Decoder
Free online JWT decoder. Inspect the header and payload of any JSON Web Token (RFC 7519). Identifies the signing algorithm and surfaces standard claims like exp, iat, sub.
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Education
English Test Score Converter
Free English test score converter. Translate TOEIC, TOEFL iBT, and IELTS scores to CEFR levels (A1-C2) using official ETS and Council of Europe concordance tables.
Showing 73–84 of 178