Free calculators that give you the answer — and show the math.
Percentages, dates, loans, BMI, passwords and more — every online calculator here is fast, private, clutter-free and free forever. Everything runs in your browser. No sign-up, ever.
Missing a calculator you need? Tell us on X — we build by request, free as always.
Most popular
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Percentage Calculator
Find X% of a number, percentage change, and more.
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Unit Converter
Length, weight and temperature between metric and imperial.
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Random Number Generator
Fair random numbers in any range, with or without repeats.
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Dice Roller
Roll a d20 with advantage, or any XdY combo — crits lit.
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Fraction Calculator
Add, subtract, multiply and divide — simplified automatically.
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Age Calculator
Exact age in years, months and days from a birth date.
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Date Calculator
Days between two dates, or add / subtract days from a date.
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Time Zone Converter
Meeting times across cities, DST handled automatically.
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Hours Calculator
Time worked minus breaks, in normal and decimal hours.
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Countdown Timer
Live countdown to any date — days, hours, minutes, seconds.
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Chess Clock
Two-player timer with increment — bullet to classical, with stats.
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Online Timer
Any countdown in one tap — presets, custom time, chime.
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Deadline Pace
What today must contain: remaining work ÷ days left.
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Notice Period
Move-out and last-day-to-send dates for 30/60/90-day notices.
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Mortgage Calculator
Payment, early payoff savings and how much you can afford.
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Debt Payoff Calculator
Snowball vs avalanche on YOUR numbers — debt-free date included.
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Amortization Calculator
Full payment schedule — interest, principal, balance, every month.
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Loan Calculator
Monthly payment, total interest and cost of any loan.
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Tip Calculator
Tip amount, total bill and split between friends.
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Subscription Cost Calculator
Your real monthly & yearly total — and what cancelling saves.
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Retirement Calculator
Nest egg at retirement — honestly, in today's dollars.
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CD Calculator
Certificate of deposit: maturity value & interest from APY.
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Compound Interest Calculator
Watch savings grow: future value with monthly contributions.
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Discount Calculator
Sale price, savings and the real total after tax.
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Auto Loan Calculator
Car payment, total interest and the real cost of the car.
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Time Card Calculator
Weekly hours from clock-in/out — overtime split and gross pay.
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Salary Calculator
Hourly, weekly, monthly and annual pay — one wage, four views.
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Savings Goal Calculator
When you'll get there, how much to save, and a reality check.
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Margin Calculator
Margin vs markup — and the price for your target margin.
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Break-Even Calculator
How many sales cover the bills — and where profit begins.
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VAT Calculator
Add or remove VAT/GST at any rate, net-VAT-gross breakdown.
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SIP Calculator
Mutual fund SIP returns in lakhs — with the growth curve.
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EMI Calculator
Loan EMI, total interest and the principal-vs-interest split.
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PPF Calculator
Tax-free maturity at 7.1% — with the ₹1.5 L limit check.
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PMI Calculator
Monthly PMI, LTV and the 80% / 78% cancellation milestones.
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Rule of 72
How fast money doubles — the shortcut and the exact answer.
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Meeting Cost
What a meeting really costs — per minute, per year, per late start.
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Split by Income
Rent and bills in proportion to income — equal sacrifice, shown honestly.
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Down Payment
Amount at any %, your saving timeline, and the 20% question.
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Savings Pace
Goal minus saved, divided by your date - monthly, weekly, daily.
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Prorated Rent
Partial-month rent by all 3 methods — the lease picks, you verify.
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FD Calculator
Fixed Deposit maturity or monthly payout — Indian quarterly compounding.
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Lumpsum Calculator
One-time investment growth — future value, gain and the ×multiple.
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Freelance Rate
Hourly rate from your income goal — three honest layers, no folklore.
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Break-Even Customers
Customers per month and day to hit zero — plus leads and budget.
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Moving Budget
The full checklist with a buffer — and your day-one cash wall.
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GPA Calculator
Grade Point Average on the 4.0 scale, course by course.
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Final Grade Calculator
What score you need on the final to hit your goal grade.
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Pomodoro Timer
Focus sprints with a chime: 25/5, 50/10 or 15/3. 🍅
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Weighted Grade Calculator
Course grade from category weights — homework, exams, final.
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Test Grade Calculator
Questions and mistakes in — percentage and letter grade out.
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Cumulative GPA Calculator
Add this semester and see your new overall GPA.
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Grade Curve Calculator
Square root, flat or high-score curve — with the exact lift.
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Percentage to GPA
Any percentage to the 4.0 scale — with the full table.
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Attendance Calculator
Your %, safe-to-miss budget, and the streak to recover.
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Random Team Generator
Split a list into fair random teams — names stay in your browser.
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Study Planner
Does your exam prep fit? Verdict, topics/day and a revision buffer.
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BMI Calculator
Body Mass Index with metric or imperial units.
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Calorie Deficit Calculator
Daily calorie target for your pace — with an honest safety floor.
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TDEE Calculator
Maintenance calories via Mifflin-St Jeor — with honest ±10% bars.
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Macro Calculator
Protein by body weight, fat for hormones, carbs fill the rest.
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Sleep Calculator
Bedtimes and alarms on the 90-minute cycle rhythm — both directions.
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Body Fat Calculator
U.S. Navy tape method — estimate, category and honest ±3–4%.
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Word Counter
Words, characters, sentences and reading time — live.
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QR Code Generator
Free QR codes that never expire, made in your browser.
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Case Converter
UPPER, lower, Title, camelCase and more — all at once.
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Words to Time
Reading and speaking time for any word count — 4 speeds compared.
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Password Generator
Strong random passwords, generated locally in your browser.
🎮 Learn by playing — 60-second games that recalibrate intuition. New: Percentage Instinct — stacked discounts vs your gut (most brains add; registers multiply). Or race the curve in the Compound Interest Race: guess when money doubles — most people lose by years. Nothing you guess is recorded.
What this site is, in one paragraph
CalcNotebook is a catalog of 70 free online calculators across finance, dates & time, math, education, text tools, health, travel and home projects — plus seven focused minute-timers, five in-depth guides and two sixty-second learning games. Every calculator shows its formula in plain text, lists its assumptions and what's not included, and cites primary sources (CFPB, WHO, CDC, RBI) where facts matter. Flagship cluster: the mortgage toolkit — payment, PITI, PMI cost and cancellation, down payment. Calculations run entirely in your browser — nothing you type is uploaded, and there is no sign-up. How we verify the math, publicly: our methodology.