Free online tools we recommend.
A curated collection of free calculators, converters, and developer utilities from our network. No signups, no paywalls — just the right tool for the job.
Calculators & Converters
Everyday math tools — percentages, ages, hours, units.
Square Footage Calculator
CalculatorCalculate square footage for rooms, lots, and irregular shapes. Supports feet, inches, meters, and yards.
thesquarefootagecalculator.com ↗Percentage Calculator
CalculatorQuickly work out percentages, percentage change, percent of, and tip/discount math.
bestpercentagecalculator.net ↗Age Calculator
CalculatorCalculate exact age in years, months, days, hours from any date of birth.
theagecalculator.net ↗Hours Calculator
CalculatorCalculate hours and minutes between two times. Useful for timesheets and payroll.
calculatehours.net ↗World Clock
Time ToolLive world clock with timezone comparison and meeting planner across cities.
clockwithus.com ↗Epoch Time Converter
Developer ToolConvert between Unix epoch timestamps and human-readable dates in any timezone.
epochtime.tools ↗Unit Cheat Sheet
ReferenceQuick reference for unit conversions — length, weight, volume, temperature, and more.
unitcheatsheet.com ↗Margin vs Markup
CalculatorConvert between profit margin and markup, find break-even, and factor in platform fees, shipping, and tax.
marginvsmarkup.com ↗Solar Calculator
CalculatorFree, unbiased solar and off-grid calculators — system sizing, savings and payback, and battery banks.
prosolarcalc.com ↗EMI Calculator (India)
CalculatorEMI for home, car, and personal loans in India, with a full amortization schedule and prepayment impact.
indiaemi.com ↗Total Interest Calculator
CalculatorTotal interest paid over the life of a loan, comparing terms and rates with a full amortization breakdown.
totalinterestcalc.com ↗SIP Calculator
CalculatorProject mutual-fund SIP returns, step-up SIPs, and goal-based investing, with maturity value and charts.
sipcalculatorhub.com ↗GPA Calculator
CalculatorCompute semester and cumulative GPA on 4.0 and weighted scales, converting letter grades and percentages.
gpacalculatorhq.com ↗Fraction Calculator
CalculatorAdd, subtract, multiply, and divide fractions with step-by-step working, simplification, and decimals.
fractionsteps.com ↗Calorie Calculator
HealthEstimate daily calorie needs, TDEE, and macros — BMR-based targets for loss, maintenance, or gain.
calorieskit.com ↗BMI & BMR Calculator
HealthCalculate BMI, BMR, and daily calorie needs in metric or imperial, with healthy-weight ranges.
bmibmrcalc.com ↗AC Tonnage Calculator
CalculatorSize an air conditioner by room area, climate, and occupancy — BTU and tonnage estimates for any space.
actonnagecalc.com ↗Voltage Drop Calculator
CalculatorVoltage drop and correct wire size for AC and DC circuits, with NEC and IEC formulas.
voltdropcalc.com ↗Solar Battery Bank Calculator
CalculatorSize an off-grid battery bank from daily load, autonomy days, and depth of discharge, with lithium presets.
solarbatterybankcalc.com ↗Backup Power Calculator
CalculatorEstimate UPS and generator runtime from load and battery capacity, for home, office, and server racks.
backuppowercalc.com ↗Cooking Measurement Converter
ConverterConvert cooking measurements between cups, grams, ounces, and millilitres, with recipe scaling.
measurechef.com ↗Construction Calculators
CalculatorA hub of construction calculators — concrete, framing, drywall, paint, and more, with material estimates.
constructioncalchq.com ↗Concrete Material Calculator
CalculatorConcrete volume plus cement, sand, and aggregate quantities — slabs, footings, and bags by mix ratio.
concretematerialcalc.com ↗Roofing Material Calculator
CalculatorRoofing squares, shingle bundles, and underlayment from area and pitch, with a waste factor built in.
roofingmaterialcalc.com ↗Stair Calculator
CalculatorStair rise, run, stringer length, and headroom to code, with a diagram for carpentry and deck building.
staircalculators.net ↗Shipping & Measurement
Closely related tools for parcel and dimension math.
DIM Weight Calculator
CalculatorDedicated dimensional weight calculator for parcel shipping and freight pricing.
dimweightcalc.com ↗Box Volume Calculator
CalculatorCalculate the volume and capacity of rectangular boxes, cylinders, and irregular shapes.
boxvolumecalculator.com ↗Tank Volume Calculator
CalculatorVolume and fill level for cylindrical, rectangular, and oval tanks — horizontal or vertical, litres or gallons.
tankvolumecalc.com ↗Cubic Yardage Calculator
CalculatorCubic yards for concrete, mulch, gravel, soil, and sand from your dimensions in any units.
cubicyardage.com ↗Pool Volume Calculator
CalculatorPool volume in gallons or litres for rectangular, round, and oval pools, with dosing help for chemicals.
poolvolumecalc.com ↗Developer Tools
Quick reference and utilities for everyday development work.
Base64 Encoder / Decoder
DecoderEncode and decode Base64 strings. Handles text, URLs, and binary file output.
base64decode.tools ↗URL Encode / Decode
Encoder / DecoderPercent-encode and decode URL components for safe transmission of special characters.
urlencodedecode.com ↗UUID Generator
GeneratorGenerate UUID v1, v4, and v7 identifiers. Bulk generation and validation supported.
www.uuidcore.com ↗JSON Tools
Formatter / ValidatorFormat, validate, minify, and diff JSON. Includes JSON-to-CSV and JSON-to-YAML converters.
jsontools.tools ↗Hash Generator
CryptographyGenerate MD5, SHA-1, SHA-256, SHA-512 and other cryptographic hashes from text or files.
hashgenerator.tools ↗Crontab Reference
Developer ToolCron expression builder and quick reference for scheduling shell jobs on Linux/Unix.
crontabsheet.com ↗Regex Guide
Developer ToolRegular expression tester, cheat sheet, and pattern library with live matching.
regexguide.com ↗CIDR Calculator
NetworkingCalculate, split, and visualize subnets. IPv4/IPv6, VLSM planner, cloud-aware reserved IPs, and Terraform export.
cidrcalculator.net ↗Subnet Mask Calculator
NetworkingNetwork and broadcast addresses, usable host range, wildcard masks, and VLSM planning for IPv4 and IPv6.
subnetmaskcalc.net ↗PDF Tools
PDF ToolMerge, split, compress, convert, and rotate PDFs in your browser — no uploads, files stay on your device.
corepdftools.com ↗Color Code Kit
Color ToolConvert between HEX, RGB, HSL, and CMYK, build palettes, check contrast, and copy ready-to-paste CSS.
colorcodekit.com ↗Barcode & QR Generator
GeneratorGenerate QR codes and barcodes (Code 128, EAN, UPC), downloadable as PNG or SVG for print and labels.
barcodeandqr.com ↗Internet Speed Test
NetworkTest download, upload, ping, and jitter right in the browser — quick, accurate, no app to install.
checkinternetspeed.tools ↗What Is My IP
NetworkSee your public IPv4 and IPv6 address, ISP, and approximate location, plus request headers.
checkmyipnow.com ↗WHOIS Lookup
NetworkLook up domain WHOIS, registrar, name servers, expiry dates, and DNS records for any domain.
whoislookuppro.com ↗Productivity & Text
Text manipulation, password security, and image tools.
Password Strength Checker
SecurityTest password strength against modern attack methods. Includes a strong-password generator.
passwordstrength.net ↗Word Counter
Writing ToolCount words, characters, sentences, and paragraphs. Reading time and keyword density too.
wordcounterfree.com ↗Text Repeater
Text ToolRepeat any string a specified number of times. Useful for testing, padding, and bulk text.
textrepeat.net ↗Case Transformer
Text ToolConvert text between upper, lower, title, sentence, camel, snake, kebab, and Pascal case.
transformcase.com ↗Picture Toolkit
Image ToolBrowser-based image tools — resize, crop, compress, convert format, and remove backgrounds.
pictoolkit.com ↗Remove Metadata
Privacy ToolStrip EXIF, GPS, and hidden metadata from images, PDFs, and Office files — locally in your browser.
removemetadata.tools ↗Number to Words
Text ToolConvert numbers to words for cheques, invoices, and legal documents, with currency wording support.
numtotext.com ↗About this network
These are independent tools we've found genuinely useful — many built by small teams who care about doing one thing well. We share traffic with them because the tools are good, not because of any commercial arrangement that compromises our recommendations.
If you run a free tool that would fit one of these categories, drop us a line at /contact. We add new tools when they meet the bar.