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🔬 ScienceFree
Limiting reactant calculator
Find the reactant that stops the reaction and the leftover of the other: 5 mol of hydrogen with coefficient 2 against 3 mol of oxygen with coefficient 1 makes…
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🔬 ScienceFree
Moles of product calculator
2.5 moles of reactant with coefficients 2 and 1 give 1.25 moles of product, through a mole ratio of 0.5.
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🔬 ScienceFree
Electrolysis overpotential calculator
Applying 2 V to a cell whose reversible decomposition voltage is 1.23 V means an overpotential of 0.77 V, the extra push your power supply delivers beyond…
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🔬 ScienceFree
Percent yield calculator
Recovering 8.5 g of product when stoichiometry predicts 10 g is an 85 % yield: enter the actual and theoretical amounts in grams, moles or any shared unit and…
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🖼️ ImagesFree
Darken a hex color by percentage
Get a deeper shade of a hex color without guessing: #4A90D9 darkened by 20 % becomes #2873C0, with the same hue and saturation and less lightness.
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🖼️ ImagesFree
RGB to CMYK converter
Get print percentages from screen colors: red 255, green 0, blue 0 becomes cyan 0 %, magenta 100 %, yellow 100 % and key 0 %.
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➗ MathFree
Binomial coefficients row
Enter a row number and receive every binomial coefficient on that line of Pascal's triangle: row 5 gives 1, 5, 10, 10, 5, 1, six exact values that never lose…
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📏 Unit convertersFree
Decibel ratio converter
A power ratio of 2 is about 3 dB. Pick power or amplitude, enter a linear ratio or a dB level, and get both forms with the right factor: 10 for power, 20 for…
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📏 Unit convertersFree
Electrical conductivity converter
1.5 S/m is 0.015 S/cm, and confusing the two shifts a reading by a factor of 100. Convert conductivity between siemens or mho per metre, centimetre and…
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📏 Unit convertersFree
Convert equivalent dose
One sievert equals 100 rem, and one millisievert is 1000 microsieverts. Convert equivalent dose between Sv, mSv, µSv and rem so old badge reports, monitor logs…
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📏 Unit convertersFree
HP to kW converter
100 hp is 74.569987158227 kW: type the horsepower from an engine, pump or motor nameplate and get kilowatts with the exact factor, plus the watts, ready for…
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📏 Unit convertersFree
Length converter
Change one measurement into another unit in a single step: 5 kilometers come out as 3.106855961187 miles.
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📏 Unit convertersFree
Convert mass moment of inertia
Convert mass moment of inertia between kg·m², g·cm² and lb·ft²: 1 kg·m² is 10000000 g·cm². Line up a European motor datasheet, a micro-gear catalogue and a US…
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📏 Unit convertersFree
Pressure gradient converter
The freshwater benchmark of 0.433 psi per foot is 9794.7175457411 pascals per meter. Convert pressure gradients between oilfield and metric units for…
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📏 Unit convertersFree
Stone to lbs converter
12 stone is exactly 168 pounds, because one stone is 14 lb. Turn a UK or Irish body weight in stone into the pounds that US apps, gym forms and shipping labels…
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📏 Unit convertersFree
Temperature converter
One converter for the four temperature scales: 100 °C is 212 °F, and every result is checked against absolute zero so an impossible reading never reaches your…
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📅 Dates & timeFree
Add working days to a date
Add or subtract working days and skip every Saturday and Sunday: 5 working days after Monday 20 July 2026 is Monday 27 July 2026.
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📅 Dates & timeFree
US daylight saving start date
In 2026, US daylight saving time starts on Sunday 8 March, when most clocks spring forward one hour at 2:00 a.m. local time.
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📅 Dates & timeFree
Days elapsed in the quarter
By 15 February 2026, 45 whole days have passed since the first quarter began on 1 January. Enter a date to see its quarter, the quarter's start and the days…
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📅 Dates & timeFree
Easter Sunday date
Easter Sunday 2026 falls on 5 April. Enter any year to get the Western Easter date, the first Sunday after the church full moon on or after 21 March, then place…
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📅 Dates & timeFree
Generation by birth year
Type a birth year and get its generation with the years that define it: 1990 is a Millennial, part of the 1981 to 1996 cohort, also called Gen Y.
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🏗️ Engineering & constructionFree
Battery runtime from Ah
Multiply the bank's amp-hours by the share you allow yourself to use, then divide by the load current: 100 Ah at 80 % usable with a 5 A load gives 80 usable Ah…
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🏗️ Engineering & constructionFree
Capacitor voltage rating selector
A 12 V rail needs a capacitor rated for at least 24 V under the default 0.5 derating factor, so the tool picks a standard 25 V part.
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🏗️ Engineering & constructionFree
Drift velocity calculator
See how slowly electrons really move in a wire: 2 A through 1 square millimetre of typical copper, with 8.5 × 10²⁸ carriers per cubic metre, drift at well under…
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🏗️ Engineering & constructionFree
Transformer turns ratio calculator
1000 primary turns and 100 secondary turns give a 10 to 1 ratio, so 240 V in becomes 24 V out. Enter the turns and one known voltage to get the missing one and…
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⚙️ Developer UtilitiesFree
Damm check digit
Add one digit to any number and catch the typos people actually make: 572 gets the Damm check digit 4 and becomes 5724, and any single wrong digit or swap of…
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⚙️ Developer UtilitiesFree
Keyword substitution cipher
With the keyword CRYPTO, Hello World becomes Btggj Vjmgp: the keyword opens the cipher alphabet, the remaining letters follow in order, and each letter is…
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⚙️ Developer UtilitiesFree
Scytale cipher
With 5 columns, HELLOWORLD becomes HWEOLRLLOD: the text is written row by row into a grid, like a strip wound round a rod, and read down each column.
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⚙️ Developer UtilitiesFree
encodeURIComponent tool
A space becomes %20, & becomes %26 and = becomes %3D, so hello world & café turns into hello%20world%20%26%20caf%C3%A9 and fits inside one query value.
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⚙️ Developer UtilitiesFree
UTF-16 code unit converter
Type Hi and get 00480069 in big-endian order, that is two code units and 4 bytes. Switch to little-endian and H becomes 48 00 instead.
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📏 Unit convertersFree
Octal to decimal converter
Octal 755 is 493 in decimal, and a mode written as 0755 gives the same answer. Every digit is checked to be 0 to 7 before anything is calculated, so a stray 8…
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📏 Unit convertersFree
Cardinal to ordinal number converter
21 becomes 21st, and the tricky teens stay right: 11th, 12th and 13th, never 11st. One rule set for rankings, race results, certificates and product copy, with…
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🧭 Travel & geographyFree
Initial bearing calculator
Leaving London for Paris along the great circle, you set off on a bearing of 148.115617°, labelled SSE on the 16-point compass.
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🧭 Travel & geographyFree
Crosswind component calculator
A 20-knot wind at 30° to the runway gives a crosswind of 10 knots and a headwind of 17.320508 knots, because the sine of 30° is one half.
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🧭 Travel & geographyFree
Geohash encoder
Turn a latitude and longitude into a short geohash: 37.7749 and -122.4194 at nine characters become 9q8yyk8yt, a key about the size of a city block that groups…
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🧭 Travel & geographyFree
Geographic midpoint calculator
The halfway point between 40.7128, -74.006 and 34.0522, -118.2437 is 39.51030757, -97.16013189: the middle of the shortest path over the globe, not a plain…
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🧭 Travel & geographyFree
Geographic polygon perimeter
The ring (0, 0), (0, 1), (1, 1), (1, 0) measures 444.763384955 km around, or 276.363154773 miles, along great-circle edges on a sphere.
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🧭 Travel & geographyFree
Pythagorean equirectangular distance
Get a quick ground distance between two nearby points by treating the map as a flat local plane: two Manhattan coordinates come out just over 5 km apart.
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➗ MathFree
Capsule volume & surface area
Get the volume, surface area and total height of a capsule, a cylinder capped by two hemispheres: a radius of 2 and a straight section of 5 give a total height…
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➗ MathFree
Hyperbola eccentricity
Measure how widely a hyperbola opens from its two semi-axes: 3 and 4 give a focal distance of 5 and an eccentricity of 5/3.
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➗ MathFree
Polygon interior angle calculator
Enter how many sides a regular polygon has and get its angles: in a pentagon the interior angles add up to 540°, each one measures 108° and each exterior angle…
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➗ MathFree
Star polygon area calculator
Get the filled area of a regular star from its number of tips, its density and the radius to the tips: the classic five-pointed star {5/2} on a circle of radius…
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➗ MathFree
Triangle incenter calculator
Find the center of the largest circle that fits inside a triangle: for the vertices (0, 0), (4, 0) and (0, 3), the incenter is (1, 1) and the inscribed circle…
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❤️ Health & fitnessFree
Mifflin-St Jeor BMR calculator
Get the modern clinical estimate of your resting calorie floor: with Mifflin-St Jeor, a 30-year-old man of 80 kg and 180 cm burns 1780 kcal a day at complete…
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❤️ Health & fitnessFree
Caffeine dose by body weight
Multiply body weight by a target in mg per kg: 70 kg at 3 mg/kg is 210 mg of caffeine. Use the rate your coach, protocol or clinician set, then compare the…
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❤️ Health & fitnessFree
eGFR kidney function calculator
A 50-year-old woman with a serum creatinine of 1 mg/dL has an eGFR of 68.6 mL/min/1.73 m², stage G2.
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❤️ Health & fitnessFree
Fat mass from body fat %
Converts a body-fat percentage into kilograms: 80 kg at 22.5% body fat is 18 kg of fat mass and 62 kg of lean mass.
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❤️ Health & fitnessFree
Ponderal index calculator
A weight of 70 kg at 1.75 m gives a ponderal index of 13.061224 kg/m³. Dividing by height cubed instead of squared ranks very tall, very short and growing…
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🏠 Home, food & hobbiesFree
Metronome subdivision calculator
At 120 BPM a beat lasts 500 ms and each sixteenth note 125 ms, which means 8 clicks every second. Enter a tempo and a subdivision such as eighths, triplets or…
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🏠 Home, food & hobbiesFree
Home circuit count calculator
A 2,000 sq ft home works out to 5 general lighting and outlet circuits at 15 A and 120 V: floor area times 3 volt-amperes per square foot, divided by what each…
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🏠 Home, food & hobbiesFree
Metal roofing panel calculator
A 1,200 square foot roof with 3 by 12 foot panels and a 0.5-foot side lap gets 30 square feet of cover per sheet, so you need 40 panels.
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🏠 Home, food & hobbiesFree
Sod calculator
A 1,000 sq ft lawn with 10% waste needs 1,100 sq ft of turf: 110 rolls of 10 sq ft, which is 3 pallets at 50 rolls each.
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➗ MathFree
Harmonic series calculator
Pick a whole number n and get the harmonic series added up to 1/n: the first 10 terms come to 2.928968253968.
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➗ MathFree
Prime factorization
Break any whole number from 2 upward into its primes: 360 is 2³ · 3² · 5, or 2, 2, 2, 3, 3 and 5 listed one by one.
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🏗️ Engineering & constructionFree
Projectile range calculator
Launch a ball from the ground at 20 m/s and 45° and see how far it lands on level ground with no air resistance, together with its time of flight and peak…
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🏗️ Engineering & constructionFree
Time of flight calculator
Three numbers decide how long a throw stays airborne when it lands at its launch height: speed, angle and gravity, for example 20 m/s at 45° under 9.81 m/s².
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🏗️ Engineering & constructionFree
Simple pendulum period
A 1 m pendulum under standard gravity of 9.80665 m/s² takes close to two seconds for a full swing there and back.
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🏗️ Engineering & constructionFree
Flywheel spin-down time
A 2 kg·m² flywheel spinning at 10 rad/s under a constant 4 N·m brake stops in 5 s, losing 2 rad/s every second.
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➗ MathFree
List all ordered compositions of an integer
The number 4 has 8 compositions, from 1+1+1+1 to 4 itself, and this tool lists every one of them in a fixed order with the count beside it.
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➗ MathFree
Discrete logarithm solver
Ask which power of 2 leaves 5 modulo 13 and you get 9, because 2^9 ≡ 5 (mod 13). Enter a base, a target and a prime modulus to find the smallest exponent, with…
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Get your key
Create an account with your email and add balance when you need it. No subscription, no sales call.
2
Call the endpoint
One authenticated POST. The API returns a task_id immediately — copy-paste snippets in five languages on every page.
3
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Receive a signed webhook the moment it's ready, or fetch a signed link. A failed task is never charged.
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On-device utilities — hash, QR, JSON, Text→PDF and more — run in your browser. No account, no limits.
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The full API — 7800+ capabilities — billed only for what you run, from $0.002 per call. No monthly fee.
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