Free online calculators & everyday tools
Fast, free calculators that work instantly in your browser. No sign-up, no downloads — and your numbers never leave your device.
All tools
Pick a tool — every one is free and works right away.
Sleep Calculator
Find the best time to go to bed or wake up, based on 90-minute sleep cycles.
MathPercentage Calculator
Work out percentages, percentage increase, decrease and discounts in seconds.
Date & TimeAge Calculator
Your exact age in years, months and days, plus days lived and next birthday.
HealthBMI Calculator
Calculate your Body Mass Index and see which healthy-weight category you fall in.
FinanceMortgage Calculator
Monthly mortgage payment with taxes, insurance and PMI, plus a full amortisation table.
FinanceLoan Calculator
Monthly loan payment and EMI, with extra-payment savings and payoff time.
EverydayTip Calculator
Work out a tip, split the bill between friends, and see what everyone owes.
WritingWord Counter
Count words, characters, sentences and paragraphs live as you type.
SecurityPassword Generator
Create strong random passwords in your browser. Nothing is sent or stored.
HealthCalorie Calculator
Daily calorie needs from the Mifflin-St Jeor equation, by activity and goal.
EducationGPA Calculator
Work out your weighted GPA on the 4.0 scale from your courses, grades and credits.
EverydayQR Code Generator
Turn any link or text into a QR code in your browser, then download it as a PNG.
MathUnit Converter
Convert length, weight and temperature instantly — miles to kilometres, kg to pounds.
Date & TimeDate Calculator
Days between two dates, or add and subtract days from any date.
FinanceCompound Interest Calculator
See how savings grow with interest, compounding and monthly contributions.
EverydayEV Charging Cost Calculator
What it costs to charge your electric car at home or in public, per month and per mile.
FinanceDebt Payoff Calculator
Compare the snowball and avalanche methods and find your debt-free date.
FinanceSavings Goal Calculator
How much to save each month to reach your goal by a date — or how long it takes.
FinanceFreelance Rate Calculator
Work out the hourly rate that covers your costs and taxes and hits your income goal.
EverydayYouTube Earnings Calculator
Estimate your YouTube AdSense earnings from monthly views, by niche and format.
EverydayAI Token Cost Calculator
Work out what your AI app costs each month in tokens, by model — GPT, Claude, Gemini.
FinanceSubscription Cost Calculator
Add up every subscription — monthly, yearly and 10-year cost — and spot the unused ones.
FinanceDropshipping Profit Calculator
Profit, margin, ROI and break-even price for a dropshipping product, in seconds.
EverydayTikTok Earnings Calculator
Estimate TikTok Creator Rewards earnings from views and your own RPM.
EverydayHeat Pump Savings Calculator
Compare a heat pump with a gas boiler on running cost and payback, for UK & EU homes.
Why use Calcly?
Instant results
Every calculator updates as you type. No waiting, no page reloads, no sign-up forms in the way.
Private by design
All calculations happen in your browser. We do not see, store or sell the numbers you enter.
Explained, not just answered
Each tool shows its formula, a worked example and answers to common questions, so you can check the result yourself.
Guides
Step-by-step guides that explain the maths behind the tools.
How to Calculate a Percentage
Find a percent of a number, work out what percent one number is of another, and handle increases, decreases and discounts.
GuideHow Much House Can I Afford?
Work out the home you can afford from your income, debts and deposit — with the 28/36 rule and worked examples.
GuideHow Many Hours of Sleep Do I Need?
Adults need 7 to 9 hours a night. Learn how 90-minute sleep cycles work and how to pick your bedtime.
How we work
Every formula on Calcly is checked against a named source — for example the Mifflin-St Jeor equation for calories and the standard amortisation formula for loans and mortgages. Health and finance tools carry clear disclaimers, and results are estimates for general information only. Each page shows its author and last-updated date.