Access a comprehensive suite of free online calculators for finance, health, fitness, and more. Precision tools designed for accuracy and ease of use.
Browse by category
Quick filters
Upload a meal photo and estimate calories with AI
Convert between steps and distance with scientific precision
Calculate maximum oxygen uptake using Rockport or Cooper test
Calculate Basal Metabolic Rate and Total Daily Energy Expenditure
Calculate body fat percentage using BMI or Navy method
Calculate your daily protein target based on weight and activity
Calculate your daily saturated fat limit for heart health
Calculate due date, trimester, and pregnancy milestones
Car payment with down payment, trade-in, tax, fees, APR, and amortization preview
PITI: principal & interest, property tax, insurance, PMI, and HOA monthly estimate
Calculate EAR/APY from nominal rates and compounding frequency
Calculate CD interest & APY returns
Calculate restaurant tips and split bills among multiple people
Add or remove sales tax to get net, tax, and total instantly
Calculate rental yield, cash flow, ROI, and investment returns
Calculate interest savings from mortgage prepayments
Calculate date differences and add/subtract days
Calculate business days between dates, excluding weekends and holidays
Convert hours and days with workday conversion and precision controls
Convert time between different time zones worldwide
Test and validate regular expressions with live results
Convert between Unix timestamps and human-readable dates
Parse and visualize HL7 v2.x messages with detailed field descriptions
Generate cryptographically secure random passwords with strength analysis
Format, validate, beautify, and minify JSON data online
Encode and decode Base64 text and files
Find your Chinese zodiac sign and characteristics
Discover your zodiac constellation and horoscope
Calculate your exact age and countdown to your next birthday
Clicks-per-second speed test with 5s, 10s, or 30s timed windows
Predict baby gender using traditional Chinese calendar
Difficulty levels, challenges, sound cue, charts & full session stats
Five red lights step on, then lights out — racing-style start reflex
Calculate semester and cumulative GPA on a 4.0 scale
Calculate aperture, shutter speed, and ISO for perfect exposure
Calculate DOF, hyperfocal distance, and background blur
Calculate equivalent focal length and field of view across sensors
Calculate flash Guide Number (GN), distance, and aperture
Calculate optimal shutter speed for freezing motion or panning
Calculate max print sizes and megapixel requirements
ONLINTools offers 64+ free, professionally designed calculators spanning health, finance, development, and lifestyle — all with instant results, zero registration, and complete privacy.
Track your health metrics with clinical-grade accuracy. Our BMI Calculator uses both WHO and Asian standards for personalized results. Pair it with the Body Fat Calculator (Navy Method) for a complete body composition profile.
Planning your diet? Start with your TDEE Calculator to find your daily calorie needs, then use the Calorie Calculator for macro splits. Our Protein Calculator helps athletes hit their daily targets. For women's health, the Ovulation Calculator tracks fertile windows, and the Ideal Weight Calculator uses 5 scientific formulas.
Make smarter financial decisions with our professional-grade tools. The Compound Interest Calculator visualizes wealth growth over time, while the Loan Calculator breaks down payments with full amortization schedules. Planning to buy a home? Use the Mortgage Prepayment Calculator to see how extra payments save thousands.
For everyday finances, our Tip Calculator handles restaurant bills, the Sales Tax Calculator adds or reverses tax from any price, and the Salary After Tax Calculator shows your true take-home pay across all 50 US states. Need wage premium estimates? Use the Overtime Calculator for time-and-a-half breakdowns.
Essential tools for IT professionals and developers. Our Subnet Calculator handles CIDR notation and IP ranges, the Regular Expression Tester provides real-time pattern matching, and the JSON Formatter beautifies and validates JSON data. Encode and decode data with our Base64 Encoder.
Designers will love the Color Converter for instant HEX/RGB/HSL conversions with color harmonies. The Scientific Calculator handles trig, log, and factorials with keyboard input. Need quick math? Try the Percentage Calculator.
Discover insights about yourself and your loved ones. The Constellation Calculator reveals your Western zodiac sign with personality insights and compatibility analysis. The Chinese Zodiac Calculator maps your birth year to one of 12 animal signs with traditional interpretations.
Celebrating a milestone? Use the Birthday Age Calculator to find your exact age in days, hours, and minutes — plus a countdown to your next birthday. Expecting parents can explore the Chinese Gender Calendar for a fun, traditional prediction tool.
Professional tools for photographers and videographers. Our Exposure Calculator helps you master the exposure triangle — find perfect aperture, shutter speed, and ISO combinations for any scene, with equivalent exposure tables and scene presets from bright daylight to starry night skies.
The Depth of Field Calculator computes precise near/far focus limits and hyperfocal distance for any camera and lens. Switching between systems? The Crop Factor Calculator converts equivalent focal length, field of view, and DOF across full frame, APS-C, Micro Four Thirds, and more.
Input your values into our clean, intuitive interface. All tools support both metric and imperial units where applicable.
Results calculate in real-time as you type. Every calculation uses peer-reviewed formulas and industry-standard methods.
Every tool includes comprehensive guides, formulas, and FAQs. Copy results or save them to your session history.
Common questions about our free online calculator suite
Yes, all 60+ calculators and tools on ONLINTools are 100% free to use with no registration, no login, and no hidden fees. Every tool works instantly in your browser.
Absolutely. All calculations are performed entirely in your browser (client-side). No personal data, inputs, or results are ever sent to our servers. Your data never leaves your device.
Our calculators use peer-reviewed scientific formulas and industry-standard methods. Health tools like BMI and TDEE use clinically validated equations (Mifflin-St Jeor, Harris-Benedict). Financial tools use standard compound interest and amortization formulas. All results are computed using IEEE 754 double-precision arithmetic.
ONLINTools offers 60+ tools across 9 categories: Health & Fitness (BMI, TDEE, body fat, calorie, ideal weight, ovulation), Finance (loan, compound interest, ROI, mortgage, salary), Developer (JSON formatter, regex tester, Base64 encoder, color converter, subnet calculator), Photography (exposure, depth of field, crop factor), Date & Time, Lifestyle, and more.
Yes. All tools are fully responsive and optimized for mobile, tablet, and desktop screens. No app installation is needed — just open your browser and start calculating.
TDEE (Total Daily Energy Expenditure) calculates the total calories you burn per day including exercise. It's essential for weight loss (eat below TDEE), muscle gain (eat above TDEE), or maintenance. Our TDEE calculator uses three BMR formulas and adjusts for your activity level.