Free Online Tools

Free Online Calculator Tools

ONLINTools is a free, English-language collection of calculators and practical guides for health, finance, photography, date and time, and developer tasks, with no account required for standard tools.

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Calculator directory

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All Categories (66)

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Health & Fitness

15 tools

Finance & Tax

19 tools

Exchange Rate ConverterConvert currencies with real-time exchange rates
Loan CalculatorCalculate monthly payment, total interest, and amortization schedule
Auto Loan CalculatorCar payment with down payment, trade-in, tax, fees, APR, and amortization preview
Mortgage CalculatorPITI: principal & interest, property tax, insurance, PMI, and HOA monthly estimate
Compound Interest CalculatorCalculate investment growth with compound interest over time

Date & Time

4 tools

Developer

6 tools

Conversion

6 tools

Photography

6 tools

Network Tools

2 tools

Lifestyle

8 tools

About the collection

Your Complete Online Calculator Suite

ONLINTools offers 66+ practical tools with clear inputs, instant results, and no registration for standard calculators. Most standard calculations run locally in your browser. Tools that require live data or AI analysis may send only the input needed to process that request.

Free Tools: 66+
Registration Needed: 0
Tools Run Locally: Most
Always Available: 24/7

Health & Fitness

Body Composition & Nutrition Calculators

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.

BMI Calculator Calorie Calculator Body Fat Calculator TDEE Calculator Protein Calculator Ideal Weight Ovulation Calculator Sleep Calculator

Finance & Investment

Investment, Loan & Tax Calculators

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, while the Salary After Tax Calculator estimates federal tax, FICA, and take-home pay. For annual tax planning, use the Federal Income Tax Calculator, or organize trips and shared bills with the Group Expense Splitter.

Compound Interest Loan Calculator ROI Calculator Mortgage Prepayment Credit Card Payoff Sales Tax Salary After Tax Federal Income Tax Group Expense Splitter Overtime Pay Rental Yield

Developer & Network

Networking, Regex & Developer Utilities

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.

Subnet Calculator JSON Formatter Regex Tester Base64 Encoder Color Converter Scientific Calculator Password Generator Bandwidth Calculator

Lifestyle & Astrology

Zodiac, Birthday & Cultural Calculators

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.

Constellation Calculator Chinese Zodiac Birthday Calculator Gender Calendar Work Days Calculator Hours to Days Calculator

Photography

Camera & Photography Calculators

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.

Exposure Calculator Depth of Field (DOF)Crop Factor & FOV Flash Range (GN)Shutter Speed Print Size

Simple by design

How Our Calculators Work

Enter Your Data

Input your values into our clean, intuitive interface. All tools support both metric and imperial units where applicable.

Get Instant Results

Results calculate in real-time as you type. Every calculation uses peer-reviewed formulas and industry-standard methods.

Learn & Share

Every tool includes comprehensive guides, formulas, and FAQs. Copy results or save them to your session history.

Common questions

Frequently Asked Questions

Common questions about our free online calculator suite

Are these online calculators really free?

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.

Is my data safe when using these calculators?

Most standard calculations run locally in your browser. Tools that require live data or AI analysis may send only the input needed to process that request. We explain these exceptions on the relevant tool and in our privacy policy.

How accurate are these calculators?

ONLINTools uses published equations and standard methods appropriate to each calculator. Important tools explain their formulas, assumptions, examples, and limitations so you can check how a result was produced. Calculator output is informational and does not replace professional medical, financial, or legal advice.

What types of calculators are available?

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.

Can I use these calculators on my phone?

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.

What is a TDEE calculator and why do I need one?

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.