Fast, free web utilities
A growing library of single-purpose tools — calculators, converters, and developer helpers — that run entirely in your browser. No accounts. No installs. No catch.
Calculators
Mortgage Calculator
Estimate monthly payments, total interest, and amortization for any home loan.
Percentage Calculator
Find a percentage, calculate percent change, and solve common percent problems.
Age Calculator
Find your exact age in years, months, and days — plus the countdown to your next birthday.
Tip Calculator
Calculate the tip and split a bill across any number of people, with smart rounding.
BMI Calculator
Calculate your body mass index in metric or imperial, with WHO category and healthy range.
TDEE Calculator
Daily calorie needs from the Mifflin-St Jeor formula, with weight-loss/gain targets.
Body Fat Calculator
US Navy method — estimate body fat from a few tape-measure readings.
Compound Interest Calculator
Project investment growth with monthly contributions and a year-by-year breakdown.
Auto Loan Calculator
Monthly car payment with down payment, trade-in, sales tax, and full payoff schedule.
Pregnancy Due Date Calculator
Estimate your due date by LMP, conception, or IVF transfer — plus current week and trimester.
Converters
Time Zone Converter
Convert any time between major world time zones, with daylight saving handled.
Unit Converter
Length, weight, temperature, volume, area, speed, and time — metric and imperial.
Color Converter
HEX, RGB, HSL, HSV, RGBA — live picker, alpha slider, lighter/darker variants.
Developer Tools
JSON Formatter & Validator
Pretty-print, minify, and validate JSON instantly — your data stays in your browser.
YAML ↔ JSON Converter
Convert YAML to JSON and back. Auto-detects direction, indentation control.
Base64 Encoder & Decoder
Encode and decode Base64 with UTF-8 and URL-safe variants. Text and files supported.
Hash Generator
MD5, SHA-1, SHA-256, SHA-384, SHA-512 of any text or file — computed locally.
JWT Decoder
Inspect the header, payload, and standard claims of any JSON Web Token.
Regex Tester
Live JavaScript regex matching with capture groups, all flags, and replace mode.
Password Generator
Cryptographically secure random passwords with entropy estimate and character-set controls.
QR Code Generator
Make QR codes for URLs, Wi-Fi, email, contacts, and more. Download as PNG.
URL Encoder & Decoder
Percent-encode and decode URLs with full-URI vs. component semantics. Query breakdown.
Unix Timestamp Converter
Convert between epoch (sec/ms) and human dates in UTC and local. Auto-detection.
Text Diff
Compare two texts side-by-side or inline at line, word, or character granularity.
Time & Productivity
Text & Writing
Word Counter
Count words, characters, sentences, and reading time in real time.
Lorem Ipsum Generator
Generate placeholder text by paragraphs, sentences, or words — plain or HTML.
Case Converter
UPPER, lower, Title, camelCase, snake_case, kebab-case, and more.
Word Unscrambler
Find every valid English word from a set of letters — Scrabble, Wordle, and crossword helper.
Markdown Previewer
Live GitHub-flavored Markdown preview with tables, fenced code, and task lists.
Why NimbleUtils?
Most "free online tool" sites are slow, ad-stuffed, and try to push you into a paid product after one click. NimbleUtils is the opposite: every tool is a single, lightweight HTML page that loads instantly and runs entirely on your device. We don't upload your inputs, we don't track your sessions, and we don't gate basic features behind a sign-up.
How we choose tools
We add a tool when it meets two simple bars: people search for it often, and the existing free options online are bloated or hard to use. Each tool gets a clean interface, accurate math, and a short explainer so you can trust the result.
Guides & explanations
Each tool ships with a short explainer, but for the topics where readers want more depth, we publish long-form guides — what is PITI, decoding a JWT safely, BMI vs body fat percentage, common regex patterns, and more.
Coming soon
Next up: slug generator, cron expression parser, image-to-base64, and CSV ↔ JSON converter. If you have a request, send it our way.