Sharp tools for everyday problems.
Free calculators, converters, and developer tools. Fast, private, no signup required.
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Math & Numbers
Percentages, averages, fractions, and more
Finance
Mortgages, loans, interest, and investments
Health & Fitness
BMI, calories, macros, and body metrics
Text & Writing
Word count, case convert, lorem ipsum
Developer Tools
JSON, Base64, UUID, hashes, and regex
Unit Conversion
Length, weight, temperature, and more
Date & Time
Age, date differences, countdowns
Image & Media
QR codes, colors, image tools
Everyday Life
Passwords, GPA, fuel costs, bill splitting
Construction & Home
Concrete, paint, square footage, and building materials
Cooking & Kitchen
Recipe scaling, unit conversion, ingredient substitution
Electrical & Electronics
Ohm's law, LED resistors, electricity costs
Science
Physics, chemistry, and scientific calculations
Sports & Fitness
Running pace, heart rate zones, one rep max
Business
Break-even, A/B testing, pricing calculations
Education
GPA, grades, and academic calculators
Color & Design
Color conversion, palettes, contrast checking
CSS & Frontend
Gradient generators, shadows, animations
PDF & Files
PDF tools, file conversion, document utilities
Randomness
Random generators, dice rolls, shufflers
Real Estate
Property calculators, rent vs buy, ROI
Automotive
Fuel economy, tire sizing, maintenance calculators
Social Media
Engagement rate, hashtag generators, post scheduling
SEO & Webmaster
Meta tags, keyword density, robots.txt testing
Legal & Documents
Document templates, legal calculations
Workflow kits
Tools bundled for specific jobs
Most popular
The most-used tools on ToolKnife
A/B Test Significance Calculator
Check if your A/B test results are significant
Break-Even Calculator
Calculate when your business breaks even
CAC Calculator
Calculate customer acquisition cost and marketing ROI
Churn Rate Calculator
Calculate customer and revenue churn rates
Conversion Rate Calculator
Calculate conversion rates and compare test variants
CV / Resume Generator
Build a professional CV and download as PDF
Email Signature Generator
Create professional email signatures instantly
Form Builder
Build and embed lead capture forms
Invoice Generator
Create and download professional PDF invoices with EU VAT support
Link Tracker
Track clicks on any URL with analytics
LTV Calculator
Calculate customer lifetime value and LTV:CAC ratio
Markup vs Margin Calculator
Compare markup and margin side by side
AI-powered tools
Powered by Claude. Deterministic tools meet AI where it matters.
AI Code Explainer
Get plain English explanations of any code
AI Text Rewriter
Rewrite text in any tone with AI
Regex Tester
Test and debug regular expressions
JSON Formatter
Format, validate, and beautify JSON data
Cron Expression Generator
Build cron expressions with a visual editor
Privacy Policy Generator
Generate a privacy policy for your website
Why ToolKnife?
Instant results
Every tool runs in your browser. No server round-trips, no loading spinners.
Private by default
Your data never leaves your device. No accounts, no tracking, no cookies.
Always accurate
Thoroughly tested formulas and algorithms. Results you can trust.
Always free
No paywalls, no premium tiers for basic tools. Free forever.
Build with ToolKnife
Connect {0} tools to your AI agent via MCP, or call them directly with the REST API. Free to start.