Free online tools,in one private place.
59 calculators and converters that open instantly and run entirely on your own device.
59 tools · 189 in-depth guides · 0 files uploaded, ever
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The four tools people open most. Change a number and the answer updates right here — open the full tool when you need the detail.
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All 40 everyday tools, grouped by what you need
Every one runs entirely in your browser, opens instantly, and asks for nothing — no email, no upload, no watermark.
Money & Finance
26 toolsWork out what you earn, owe, and pay — before you sign anything.
Salary Calculator
Convert your pay between hourly, weekly, bi-weekly, semi-monthly, monthly, and annual — and see your estimated take-home pay after income tax and social contributions. Country presets for the US, UK, Canada, Australia, and India with current tax rules. 100% private.
Loan Calculator
Calculate the monthly payment, total interest, total cost, and full amortization schedule for any personal or auto loan. See how an extra monthly payment cuts interest and payoff time. Multi-currency (USD, GBP, EUR, CAD, AUD, INR).
Loan Comparison
Compare two or three loan offers side by side and rank them by what they really cost — total interest plus every fee — with an effective APR that accounts for fees. Multi-currency, 100% private.
Mortgage Calculator
Estimate your monthly mortgage payment with a full PITI breakdown — principal, interest, property tax, insurance, PMI, and HOA. See total interest, payoff date, an amortization schedule, and how extra principal payments save. 100% browser-based.
Retirement Calculator
Project your retirement pot and the income it could support, shown in today's money so the number actually means something. Set your own return and inflation assumptions and watch how much the answer moves.
Emergency Fund
List your bank balances and monthly expenses to see how many months you are covered for, how far you are from a 3- or 6-month fund, and what to save each month to get there. Your figures stay on your device and are remembered for next time.
Freelance Rate
Work out the hourly and day rate you need to charge to reach a target take-home income, once holidays, sick days, unbillable admin time, business overheads and a tax set-aside are accounted for. Shows where every hour of your rate actually goes.
Break-Even
Work out how many units you must sell before a product turns a profit, with itemised fixed costs, contribution margin, margin of safety and a target-profit mode. A sensitivity table shows what happens to break-even when price or unit cost moves.
Margin & Markup
Calculate margin, markup and selling price from any two of cost, price and percentage, with both figures always shown side by side so the two are never confused. Adds marketplace fees and overheads to give the net margin, and blends several products into a weighted overall margin.
Budget Planner
Split your take-home pay across needs, wants and savings using the 50/30/20 guideline or your own percentages, then enter what you actually spend and see where the plan and reality part company. Saved on your device for next time.
Car Affordability
Turn a monthly budget into the car price you can actually afford, counting insurance, fuel, servicing, tax and depreciation rather than the loan payment alone. Works the other way too, from a car price to what it really costs each month.
Savings Goal
Work out what to save each month to hit a target by a date, how long a given monthly amount will take, or what you end up with. Handles a starting balance and optional interest, and flags a plan that would take an unrealistic share of your income.
Credit Card Payoff
See how long a credit card balance takes to clear and what the interest costs, comparing a fixed payment against minimum payments. Handles several cards at once and ranks avalanche against snowball so you can see which order actually costs less.
Sales Tax
Add sales tax to a price or work backwards from a total to the pre-tax amount, with state base rates as a starting point. Handles several items at once, flags tax-exempt lines, and shows the combined state plus local rate you actually pay.
Tip Calculator
Work out the tip and what each person owes, including uneven splits where people ordered different amounts. Round up to a clean number, choose whether the tip goes on the pre-tax or post-tax bill, and see the effective percentage either way.
Rent vs Buy
Work out the year at which buying a home overtakes renting, counting the costs both sides actually incur — including the return the renter earns by investing the deposit they never spent.
Inflation Calculator
See what inflation does to a sum of money: purchasing power over time, what you would need later to match today, and whether your savings rate is actually keeping up in real terms.
Compound Interest
Calculate compound interest and investment growth with optional monthly or annual contributions, any compounding frequency, and multiple currencies. See final balance, total interest, and a year-by-year table.
Fuel Cost Calculator
Compare the real running cost of Petrol, Diesel, CNG, and Electric (EV) for the same driving — broken down by day, week, month, and year. Country presets for the US, UK, Canada, Australia, India, and Germany with editable local prices. Multi-currency, 100% private.
EMI Calculator
Calculate home loan, car loan, or personal loan EMI with full repayment schedule. Add part payments to see interest saved and tenure reduced. 100% browser-based.
Invoice Generator
Create a clean, professional invoice in your browser and save it as a PDF. Line items, tax, discounts, payment terms, and six currencies — no sign-up, no watermark, and nothing is uploaded.
Percentage Calculator
Work out any percentage question: X% of Y, what percent one number is of another, increases and decreases, adding or removing a percentage, and reverse percentages. Shows the formula, not just the answer.
Discount Calculator
Work out sale prices, stacked discounts, and what you actually saved. Shows why 30% off then 20% off is 44% off and not 50%, handles tax, and compares unit prices so you can tell a real deal from a badly-worded one.
Income Tax
Calculate income tax for FY 2025-26 (AY 2026-27). Compare old vs new tax regime instantly. Includes standard deduction, 80C, HRA, and all major deductions for salaried Indians.
GST Calculator
Calculate GST instantly — add GST or extract GST from inclusive amounts. Supports the GST 2.0 slabs (0%, 5%, 18%, 40%) with CGST/SGST/IGST split. Free and Indian-business friendly.
Amount to Words
Convert amounts to words for cheques, invoices, and legal documents. Supports USD, INR, EUR, GBP with Lakhs and Crores.
Everyday & Health
7 toolsQuick answers for dates, ages, health numbers, and time.
Calorie Calculator
Work out your BMR, TDEE, and a daily calorie target for losing, maintaining, or gaining weight — plus a macro breakdown. Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle, in metric or imperial.
BMI Calculator
Calculate your Body Mass Index instantly. Supports metric (kg/cm) and imperial (lbs/ft) units. See BMI category, healthy weight range, and ideal weight for your height.
Unit Converter
Convert length, weight, temperature, volume, area, speed, digital storage, and time between metric and imperial units. Every conversion factor follows the international definition, and exact factors are marked as exact.
Age Calculator
Calculate exact age in years, months, and days from any date. See total months, weeks, days, hours, and minutes lived. Perfect for documents, birthdays, and milestones.
Date Difference
Calculate days, weeks, months, and years between two dates. Add or subtract days from a date. Perfect for project planning, deadlines, and event countdowns.
Time Converter
Convert between 24-hour and 12-hour time formats instantly. Supports bulk conversion and military time.
Timestamp Converter
Convert Unix epoch time to a human date and back, in seconds, milliseconds, microseconds, or nanoseconds. Auto-detects the unit, shows ISO 8601 and local time, and handles dates before 1970.
Photos, Files & Text
7 toolsShrink, convert, count, and create — without uploading anything.
Image Compressor
Compress JPG, PNG, and WebP images up to 95% smaller without visible quality loss. Reduce file size for WhatsApp, email, and websites — 100% browser-based, your photos stay private.
Image Resizer
Resize images to exact dimensions, a percentage, or inside a bounding box, with presets for social and web. Downscales in steps for a cleaner result, and warns rather than silently blurring when you ask to enlarge.
PDF Tools
Merge multiple PDFs into one, split a PDF into pages, or compress PDF size — all in your browser. No uploads, no signups, completely private and free.
QR Code Generator
Generate QR codes for URLs, text, WiFi, email, and phone numbers. Customize colors and size, then download as PNG.
Word Counter
Count words, characters, sentences, and paragraphs. See reading time, speaking time, and keyword density.
Color Picker
Pick colors and convert between HEX, RGB, HSL, and CMYK formats. Check contrast ratios for accessibility.
Embroidery Viewer
Preview DST embroidery design files online. View stitch patterns, colors, dimensions, and download as PNG or PDF.
Want a Loan at a Lower Interest Rate?
Home · Personal · Car · Education · Business · Gold. Our free guide explains what actually sets your rate, how to compare banks & NBFCs on total cost — not the headline number — and how to check any offer with free calculators.
Writing code instead? 24 developer tools live over here.
JSON, YAML and CSV converters, a regex tester, a diff checker, an in-browser API client, hashes and Base64 — the same privacy rules, nothing uploaded, no sign-up.
Nothing Leaves Your Device
Your salary, your photos, your documents — everything is processed on your own machine. There is no upload step, because there is no server to upload to.
Instant, Every Time
No queues, no "processing…" spinner, no waiting for a download link by email. Results appear as fast as you can type, even on a slow connection.
Explained, Not Just Calculated
Every calculator comes with a plain-English guide, worked examples, and reference tables — so you understand the answer, not just read it.
Why use StringToolsApp?
Most online tools make you pay for the privilege of being interrupted. You search for something simple — how much a job offer is really worth after tax, or how to get a holiday photo under an email attachment limit — and land on a page buried in pop-ups that wants your email address before it will show you an answer. Worse, plenty of them ask you to upload the file first, which means your payslip or passport scan has just been copied onto somebody else’s server.
StringToolsApp works the other way round. Every tool here runs entirely inside your own browser using modern web technology, so the numbers you type and the files you open stay on your device. Nothing is uploaded, nothing is stored, and closing the tab is all it takes to erase it. That is also why the tools are fast: there is no round trip to wait for.
We also think a calculator that only spits out a number is half a tool. Each page pairs the working tool with a genuine guide — how the maths actually works, worked examples, reference tables, and honest notes about what the result does not include. Whether you need a take-home pay calculator, a loan calculator, an image compressor, or PDF tools, the goal is that you leave understanding the answer.
Building something instead? The developer tools section has the JSON, YAML, regex, diff, hashing, and API utilities — same rules, same privacy, no sign-up.