Developer Utilities
Small developer utilities that save a trip to a random website. Encode and decode Base64, explain a regex, build UTM links, generate QR codes and vCards, and more — the everyday helpers. Free in your browser, and available by API when you need them in a script.
Developer Utilities
Darken a hex color by percentage
lower lightness, free
POST /color/darken$0.002Developer Utilities
RGB to CMYK converter
print percentages, free online
POST /color/rgb-cmyk$0.002Developer Utilities
Binomial coefficients row
n choose 0…n as BigInt, free
POST /combo/binomial-row$0.002Developer Utilities
Decibel ratio converter
dB to power or amplitude linear ratio
POST /conv/decibel-ratio$0.002Developer Utilities
Electrical conductivity converter
S/m, S/cm, mho/m, free
POST /conv/electrical-conductivity$0.002Developer Utilities
Convert equivalent dose
Sv, mSv, µSv, rem, free
POST /conv/equivalent-dose$0.002Developer Utilities
HP to kW converter
horsepower to kilowatts, exact factor
POST /conv/hp-to-kw$0.002Developer Utilities
Length converter
meters, km, miles, feet, inches, yards
POST /conv/length$0.002Developer Utilities
Convert mass moment of inertia
kg·m², g·cm², lb·ft², free
POST /conv/moment-of-inertia$0.002Developer Utilities
Pressure gradient converter
Pa/m, psi/ft, bar/m and more
POST /conv/pressure-gradient$0.002Developer Utilities
Stone to lbs converter
exact 14 lb factor, free online
POST /conv/stone-to-lbs$0.002Developer Utilities
Temperature converter
Celsius, Fahrenheit, Kelvin, Rankine
POST /conv/temperature$0.002Developer Utilities
Add working days to a date
skip weekends, free
POST /date/add-workdays$0.002Developer Utilities
US daylight saving start date
second Sunday of March, free
POST /date/daylight-saving-start-us$0.002Developer Utilities
Days elapsed in the quarter
count whole days from quarter start
POST /date/days-elapsed-quarter$0.002Developer Utilities
Easter Sunday date
Gregorian computus for any year
POST /date/easter$0.002Developer Utilities
Generation by birth year
Millennial, Gen Z, Boomer and more
POST /date/generation-cohort$0.002Developer Utilities
Battery runtime from Ah
capacity, load current, and usable DoD
POST /elec/battery-runtime-ah$0.002Developer Utilities
Capacitor voltage rating selector
derate working voltage to a standard rating
POST /elec/capacitor-voltage-rating$0.002Developer Utilities
Drift velocity calculator
find vd from current, n, A and q
POST /elec/drift-velocity$0.002Developer Utilities
Transformer turns ratio calculator
Np/Ns and voltages, free
POST /elec/transformer-turns$0.002Developer Utilities
Damm check digit
compute and validate, catch typos free
POST /enc/damm$0.002Developer Utilities
Keyword substitution cipher
encrypt & decrypt online, free
POST /enc/keyword-cipher$0.002Developer Utilities
Scytale cipher
encrypt or decrypt with a column transposition
POST /enc/scytale$0.002Developer Utilities
encodeURIComponent tool
encode and decode URI components, free
POST /enc/url-component$0.002Developer Utilities
UTF-16 code unit converter
encode or decode hex, free
POST /enc/utf16$0.002Developer Utilities
Octal to decimal converter
base-8 string to integer, free
POST /fmt/octal-decimal$0.002Developer Utilities
Cardinal to ordinal number converter
1st, 2nd, 3rd, free
POST /fmt/ordinal$0.002Developer Utilities
Initial bearing calculator
forward azimuth between two coordinates
POST /geo/bearing$0.002Developer Utilities
Crosswind component calculator
wind speed and angle, free
POST /geo/crosswind-component$0.002Developer Utilities
Geohash encoder
latitude and longitude to a compact string
POST /geo/geohash-encode$0.002Developer Utilities
Geographic midpoint calculator
great-circle halfway point free
POST /geo/midpoint$0.002Developer Utilities
Geographic polygon perimeter
great-circle length of a lat/lon ring
POST /geo/polygon-perimeter$0.002Developer Utilities
Pythagorean equirectangular distance
approximate ground metres between two points
POST /geo/pythagorean-geo-distance$0.002Developer Utilities
Capsule volume & surface area
stadium of revolution, free
POST /geom/capsule$0.002Developer Utilities
Hyperbola eccentricity
from semi-axes a and b, free
POST /geom/hyperbola-eccentricity$0.002Developer Utilities
Polygon interior angle calculator
sum, exterior & per-angle
POST /geom/polygon-interior-angle$0.002Developer Utilities
Star polygon area calculator
regular {n/d} area from points, density, radius
POST /geom/star-polygon-area$0.002Developer Utilities
Triangle incenter calculator
incenter and inradius from vertices
POST /geom/triangle-incenter$0.002Developer Utilities
Mifflin-St Jeor BMR calculator
basal metabolic rate from weight, height, age and sex
POST /health/bmr-mifflin$0.002Developer Utilities
Caffeine dose by body weight
mg from mg/kg target, free
POST /health/caffeine-per-kg$0.002Developer Utilities
eGFR kidney function calculator
CKD-EPI creatinine free
POST /health/egfr$0.002Developer Utilities
Fat mass from body fat %
convert weight and percent to kg
POST /health/fat-mass-from-percent$0.002Developer Utilities
Ponderal index calculator
mass over height cubed, free
POST /health/ponderal-index$0.002Developer Utilities
Metronome subdivision calculator
duration in ms and frequency from tempo
POST /hobby/metronome-subdivision$0.002Developer Utilities
Home circuit count calculator
lighting & outlets from sq ft
POST /home/circuit-count$0.002Developer Utilities
Metal roofing panel calculator
panels from roof area and overlap
POST /home/metal-roofing-panels$0.002Developer Utilities
Sod calculator
rolls and pallets from lawn area and waste
POST /home/sod$0.002Developer Utilities
Harmonic series calculator
n-th partial sum H_n
POST /math/harmonic-series$0.002Developer Utilities
Prime factorization
break any integer into primes and exponents
POST /math/prime-factorization$0.002Developer Utilities
Projectile range calculator
speed, angle and gravity, free
POST /mech/projectile-range$0.002Developer Utilities
Time of flight calculator
projectile launch speed, angle, gravity
POST /mech/projectile-time-of-flight$0.002Developer Utilities
Simple pendulum period
T = 2π√(L/g) online
POST /mech/simple-pendulum$0.002Developer Utilities
Flywheel spin-down time
inertia, speed, and braking torque
POST /mech/spin-down-time$0.002Developer Utilities
List all ordered compositions of an integer
free
POST /numth/compositions-list$0.002Developer Utilities
Discrete logarithm solver
baby-step giant-step mod p
POST /numth/discrete-log$0.002Developer Utilities
Divisors of a number
list, count and sum, free
POST /numth/divisor-list$0.002Developer Utilities
Is prime checker
trial division and Miller–Rabin, free
POST /numth/prime-checker$0.002Developer Utilities
Acoustic resonance Q factor calculator
f0 over half-power bandwidth
POST /optics/acoustic-resonance-q-factor$0.002Developer Utilities
Lensmaker's equation
focal length from n, R1, R2
POST /optics/lensmaker$0.002