Free Online Calculators & Converters
34 fast, free tools — number-base converters, finance & mortgage calculators, unit converters, health calculators, and developer utilities. No sign-up, no clutter; everything runs right in your browser.
Base Converter
Convert between binary, decimal, hex, and other number bases
Percentage Calculator
Calculate percentages with 5 modes: percentage of number, X is what % of Y, increase/decrease, difference, and reverse percentage
Quadratic Equation Solver
Solve quadratic equations ax² + bx + c = 0 with step-by-step solutions, discriminant analysis, and visual parabola graph
Mortgage Calculator
Calculate monthly payments and amortization schedules
Compound Interest
Calculate investment growth with compound interest
Loan Prepayment Calculator
See how extra payments save money and time on loans
Prepayment vs Refinance Calculator
Compare prepayment vs refinancing strategies
Car Buy vs Lease Calculator
Compare monthly payments, total costs, break-even points, and get recommendations based on your driving habits
Solar Panel ROI Calculator
Calculate solar panel costs, savings, and ROI. Get payback period, 25-year projections, and environmental impact estimates
Physics Unit Converter
Convert force, energy, speed, and power units
Color Converter
Convert RGB, Hex, HSL and generate color palettes
ASCII Table
View ASCII character codes in multiple formats
Grade Calculator
Calculate weighted grade averages
GPA Calculator
Calculate GPA with plus/minus grades
Final Grade Calculator
Find the grade needed on your final exam
Turtle Graphics
Learn programming by drawing with turtle graphics commands
BMI Calculator
Calculate Body Mass Index and healthy weight range
Glucose to A1C Converter
Convert between blood glucose and HbA1c values
Kids Growth Calculator
Calculate child height/weight percentiles (WHO standards)
Penile Percentile Calculator
Calculate percentiles based on medical research data
Penis Size Percentile Chart
Length, girth & volume at every percentile (reference chart)
Age Calculator
Calculate your exact age and days until next birthday
JSON Validator
Validate, format, and minify JSON with error detection
Password Generator
Generate strong, secure passwords with customizable options
Base64 Encoder/Decoder
Encode and decode Base64 strings with file support
Markdown Editor
Professional markdown editor with live preview and document management
Mermaid Diagram Editor
Advanced Mermaid diagram editor with beautiful themes, real-time preview, and export options
API Rate Limit Calculator
Calculate optimal rate limits for APIs. Supports multiple strategies and generates Nginx, Kong, AWS configurations
System Latency Budget Calculator
Allocate latency budgets across frontend, backend, network, database layers. Track P95 performance targets and identify bottlenecks
Kafka Message Size Calculator
Calculate Kafka message size including overhead, batch size, compression, and throughput estimation
Jira Story Points Calculator
Calculate agile story points using Fibonacci sequence. Input complexity, effort, and risk factors to get recommended point values
LLM Token Budget Calculator
Calculate LLM API costs for 50+ models. Estimate token usage, daily/monthly costs, and find cheaper alternatives
LLM Self-Hosted vs API Calculator
Calculate when self-hosting an LLM pays off vs using cloud APIs. Compare costs for GPT-4, Claude, Llama, and more
DORA Metrics Calculator
Measure DevOps performance with the four DORA metrics: deployment frequency, lead time, change failure rate, and time to restore
