Tiny, focused tools that load fast and get out of your way.
Calculate age from birthdate.
Days between two dates.
Compute body mass index (BMI) from height and weight.
Tip + split the bill.
Increase/decrease from A to B.
Monthly payment for a loan.
Future value with periodic compounding.
Resize dimensions and simplify ratios.
Compute pixels per inch from pixel dimensions and diagonal size.
Convert Unix time to date and back.
Celsius, Fahrenheit, Kelvin.
Convert numbers between binary, octal, decimal and hexadecimal.
Compute savings and final price after discount.
Add tax to price.
Extract VAT from total.
Price per unit.
Interest without compounding.
Compound annual growth rate.
Return on investment.
Solve any of the three.
Roman ↔ Integer.
Compute area and circumference from radius or diameter.
Find the missing side.
Add or subtract years, months, and days to a date.
Compute greatest common divisor and least common multiple.
Convert annual salary to hourly and back.
Payment, payoff time, and total interest.
Months to pay off a loan with a given payment.
Net present value of cash flows.
APR ↔ monthly rate (effective).
Internal rate of return.
mph ↔ km/h ↔ m/s.
Units and sales needed to cover fixed costs.
Add HH:MM:SS durations.
Convert margin and markup; compute price.
X% of Y.
Convert between decimal and fraction, reduced to lowest terms.
Doubling time estimate.
Decimal ↔ scientific (E) notation.
Factorization & divisor count.
Solve ax²+bx+c=0.
Solve a:b = c:x.
Population or sample standard deviation.
Find weekday from date.
Standardize a value given μ and σ.
Entropy & brute‑force time (client‑side).
Mifflin‑St Jeor BMR and estimated daily calories by activity (TDEE).
Estimate body fat using the US Navy circumference method.
Convert between mpg (US/Imp), L/100 km, and km/L.
Compute GPA from course credits and letter grades (unweighted).
Right circular cylinder formulas.
Surface area and volume.
WCAG contrast for text/background pairs.
Convert colors and preview.
Convert HEX and HSL.
Mix two colors (linear sRGB option).
Complement, triad, analogous.
WCAG contrast grid for many colors.
Generate a color ramp from a base color.
Color difference (CIEDE2000).
Compute sRGB relative luminance (WCAG).
Convert color temperature to sRGB.
Convert between RGB and CMYK.
Search MDN named colors list.
Convert CSS HWB to RGB.
Create QR codes for text, URLs, or Wi‑Fi.
Join a Wi‑Fi network with a scan.
Contact card as a QR code.
Calendar event in a QR code.
geo: latitude/longitude QR (RFC 5870).
mailto: email QR (RFC 6068).
sms: opens SMS composer (platform‑dependent).
tel: opens dialer (RFC 3966).
Encode any text or link into a QR.
Compact contact card (MECARD).
Bitcoin payment URI (BIP‑21).
Ethereum payment URL (EIP‑681).
Click‑to‑Chat link (wa.me).
Convert between ASCII and Unicode escapes.
Words, chars, lines, sentences.
Uppercase, lowercase, Title, sentence.
Make clean slugs; URL encode/decode.
Base64 ↔ UTF‑8 text.
Find/replace with RegExp support.
Convert between CSV and JSON.
Test JavaScript regular expressions.
Sort, unique, trim lines of text.
Inspect URL parts and query params.
Generate RFC 4122 UUID v4.
Simple cipher transforms.
Encode/decode International Morse.
Line‑by‑line diff viewer.
25/5 focus timer in your browser.
Start, stop, reset, laps.
Count down to duration or time.
Alternate work/rest for N rounds.
Create multiple labeled countdowns.
Simple web metronome (Web Audio).
Unix seconds ↔ ISO timestamp.
Find rhymes (basic, offline list).
Count words and sort by frequency.
English letter points.
Is it a palindrome?
Flesch–Kincaid, Fog, SMOG (approx).
Check if a sentence uses all letters.
Edit distance between strings.