Small tools that
answer one question fast.
ecech. is a growing library of free, single-purpose online calculators and developer utilities. No signup, no clutter, no data collection — every tool runs entirely in your browser.
Popular right now
See all →1099 vs W-2
Going contract means picking up both halves of payroll tax, losing paid leave, and buying your own benefits. The rate has to move a long way to break even.
Finance🛒Amazon FBA Calculator
Referral fee, fulfilment fee by size tier, monthly storage, returns and ad spend — subtracted in the order Amazon actually applies them, down to profit per unit.
E-commerce💻Base64 Encode / Decode
Text or files, both directions, with correct UTF-8 handling and a URL-safe toggle — plus the 33% size penalty shown before you paste a 4 MB image into a JSON payload.
Developer💰Split the Bill
100 divided by three is 33.33 each, which totals 99.99. This hands out the leftover pennies so the parts match the bill exactly.
Finance🏃BMI Calculator
Your BMI, your category, the healthy weight range for your height — and an honest account of the four situations where BMI gives the wrong answer about you.
Health💰Bonus Withholding
22% federal plus 7.65% payroll is 29.65% before state tax. It is a deposit against your real bill, and it settles at filing either way.
FinanceBrowse by category
Ten focused collections, each built around a specific job to be done.
Financial & Currency
Currency conversion with real fees baked in, loan and interest maths, margin and payroll checks — the numbers that decide whether a deal is worth doing.
English Exams & Writing
Score conversions, writing checks and timing tools for IELTS, TOEFL and TOEIC — the parts of preparation that are arithmetic rather than practice.
Developer & Code
Formatters, validators, encoders and generators that save you from installing another dependency just to check one string.
Text & SEO Content
Counters, case converters, density analysers and readability checks for anyone whose words have to hit a limit or rank on Google.
Network & IP
Subnet maths, IP lookups, encoders and password generation — the sysadmin sidebar you keep open in a second tab.
Date, Time & Timezone
Timestamps, business-day maths and meeting windows that actually respect daylight saving in every city involved.
E-commerce & Pricing
Landed cost, marketplace fees, break-even discounting and ad profitability — pricing tools that subtract before they add.
Math & Statistics
Percentages, averages, deviation, significance and ratio maths, each with the working shown rather than just an answer.
Design & Color
Colour conversion, contrast auditing, palette building and CSS generators that output code you can paste straight into a stylesheet.
Health & Fitness
Body metrics, energy balance, hydration and pace calculators using published formulas, with the assumptions stated openly.
YouTube Creator Tools
Loop a section, pull a video ID out of any link, shift a whole subtitle file, build an embed — the small jobs that sit between filming and publishing.
Image & Photo Tools
Compress, convert, resize, crop and strip metadata entirely inside your browser. Your photos are never uploaded, because there is no server to upload them to.
Productivity & Units
Storage, speed, length, weight and paper-size conversion for the moments a spec sheet and your reality use different units.
Home & Construction
Material quantities, coverage rates and running costs for real projects — the waste factor, the rounding up to whole bags, and the units that quietly differ between the label and the job.
Latest tools
New utilities ship every week.
App Store Listing
Check app name, subtitle, promotional text, description and the keyword field's easily missed 100-byte limit.
Text & SEO💻CSV to JSON
Leading zeros are identifiers, long digit strings lose precision as numbers, and 03/04/2026 has two readings. This infers types and knows where to stop.
Developer💬Topic Sentence Extractor
Strips out every paragraph body and leaves only the opening sentences. If they do not make an argument by themselves, neither does the essay.
English💰Auto Loan
The longer term buys a smaller payment with time spent owing more than the car is worth. That gap is only invisible until you have to sell.
Finance🏠Grass Seed
Rates run from 0.5 to 8 lb per thousand square feet depending on the species, and overseeding is half of new seeding. One number cannot cover that.
Home📏Pan Converter
Batter fills area, and area goes with the square of the radius. To double an 8 inch round you need 11.3 inches, not 16.
Converters🎥Timestamp Link
Paste almost any YouTube URL, enter a time, and get a clean share link that opens at that exact moment.
YouTube🎥YouTube Video ID
Paste any YouTube link — watch, youtu.be, embed, Shorts, live, with or without a playlist attached — and get the clean 11-character ID plus every other URL form.
YouTubeWhy ecech. exists
Most online calculators are the same three form fields wrapped in six advertisements and a cookie wall. They answer the textbook version of a question and ignore the version you actually have: not “what is 100 USD in euros” but “what will my card actually charge me after the foreign transaction fee”; not “what is 30% of 40” but “what discount can I run and still clear my target margin after marketplace fees”.
Every tool here is built around one of those realistic questions. Each one loads as a single self-contained page, runs entirely in your browser, keeps no account, sets no tracking cookie and sends none of your inputs to a server. Each one also shows its working — the formula, the assumptions and the edge cases — so you can check the result rather than trust it blindly.
- One job per page. No mega-calculator with 40 tabs.
- Real-world inputs. Fees, taxes, rounding and regional variants included where they matter.
- Shown working. Formulas and assumptions are printed next to the answer.
- Fast everywhere. Single file, no framework, usable on a phone on bad hotel wifi.