Free online tools that just work

56 calculators and utilities plus a live air-quality tracker. No sign-up, no uploads, no waiting: everything runs right in your browser.

Air Quality in Cigarettes Finance Calculators Health & Fitness Date & Time Fun & Curious Text Tools Unit Converters Math & Education Web & Developer

Live · any city in the world

How many cigarettes is your air today?

Today's PM2.5 pollution in your city, translated into cigarettes smoked. Updated hourly, with a shareable card.

Finance Calculators

All finance tools

Compound Interest Calculator See how savings grow with compound interest and regular contributions. Cost of Smoking Calculator What a smoking habit costs a year, and what quitting is worth. Credit Card Payoff Calculator How long a card balance takes to clear, and what it costs. Discount Calculator Sale price, money saved and stacked discounts in one go. FIRE Calculator Your financial independence number and how long it takes. Fuel Cost Calculator What a trip costs in fuel, per person and per month. Inflation Calculator What an amount from any year is worth in today's money. Loan Payment Calculator Monthly payment, total interest and a full amortization schedule. Salary to Hourly Calculator Convert yearly salary to hourly, daily, weekly and monthly pay (and back). Sales Tax and VAT Calculator Add tax to a net price or strip it out of a gross one. Savings Goal Calculator How much to save each month, or how long your plan will take. Tip Calculator Tip amount, total bill and the split per person in seconds. When Will I Be a Millionaire? The exact date your savings reach one million at your current pace.

Health & Fitness

All health tools

BMI Calculator Body mass index, weight category and your healthy weight range. Body Fat Calculator Body fat percentage from tape measurements, US Navy method. Caffeine Half-Life Calculator How much caffeine is still in your system, and when it is low enough to sleep. Calorie Burn Converter One slice of pizza = how many minutes of running, burpees or walking? Heart Rate Zone Calculator Your five training zones in beats per minute. Ideal Weight Calculator Healthy weight range from four classic formulas plus BMI. Macro Calculator Protein, carbs and fat in grams from your calorie target. Pregnancy Due Date Calculator Due date, current week and the trimester milestones. Running Pace Calculator Pace per km and mile, speed, and predicted 5K to marathon finish times. Sleep Cycle Calculator The best times to fall asleep or wake up so you finish a full sleep cycle. Steps to Calories Calculator Calories burned and distance covered by your daily steps. TDEE and BMR Calculator Daily calories to maintain, lose or gain weight. Water Intake Calculator How much water you should drink per day based on weight, activity and climate.

Date & Time

Age Calculator Your exact age in years, months and days, plus days until your next birthday. Date Duration Calculator Days, weeks, months and business days between two dates. Daylight Saving Time Checker When do the clocks change next in your time zone, and which way?

Fun & Curious

Age on Other Planets How old you would be on Mars, Jupiter and every other planet. Cat Years Calculator Your cat's age in human years and its current life stage. Dog Years Calculator Your dog's age in human years, adjusted for breed size. Life in Seconds How many seconds, heartbeats and breaths you have lived so far. Password Crack Time Calculator How long would it take a hacker to crack your password? Find out instantly.

Text Tools

Word Counter Count words, characters, sentences and reading time. Case Converter Convert text to UPPER, lower, Title, camelCase and more. Lorem Ipsum Generator Generate placeholder paragraphs, sentences or words. Text Diff Checker Compare two texts and highlight the differences. Remove Duplicate Lines Delete repeated lines and clean up lists. Sort Lines Sort lines alphabetically, numerically or reverse them. URL Slug Generator Turn any title into a clean, SEO-friendly URL slug.

Unit Converters

All convert tools

Area Converter Square metres, square feet, acres and hectares converted instantly. Cooking Measurement Converter Cups, spoons, millilitres and fluid ounces for recipes. Length Converter Convert metres, feet, inches, miles and kilometres in one place. Speed Converter km/h, mph, m/s, knots and mach converted in one step. Temperature Converter Celsius, Fahrenheit, Kelvin and Rankine in one conversion. Volume Converter Litres, gallons, pints, cups and cubic metres converted instantly. Weight Converter Kilograms, pounds, stones, ounces and tonnes converted instantly.

Math & Education

Final Grade Calculator The score you need on the final exam to hit your target grade. Fraction to Decimal Converter Convert fractions to decimals and percentages, and back again. GPA Calculator Grade point average from up to six courses, weighted by credits. Percentage Calculator Four percentage questions answered, with the working shown. Ratio Calculator Simplify a ratio, split a total, or solve A:B = C:D. Roman Numeral Converter Numbers to Roman numerals and Roman numerals back to numbers.

Web & Developer

Data Storage Converter Bytes, KB, MB, GB, TB and the binary KiB, MiB, GiB units. Number Base Converter Binary, octal, decimal and hexadecimal in one conversion.

Why use ToolNest?

Most "free online tools" send your data to a server, bury the result under pop-ups and make you wait. ToolNest takes a different approach: every tool is a small, self-contained web app that runs completely inside your browser. That makes it fast, it keeps working offline once the page has loaded, and it means the numbers, passwords and dates you type never leave your device.

Built for everyday questions

What will this loan cost me? How old am I in days? When should I go to bed to wake up refreshed? How strong is my password? Is the air outside safe today? Each tool answers one question well, explains the formula behind it, and answers the follow-up questions people usually have.

Free, with no account

There is nothing to install and no sign-up. The site is supported by unobtrusive advertising so that every tool can stay free. If you have an idea for a tool you would like to see, please get in touch.