Tools

Pilots and weather

Flight-planning sums, a METAR decoder, and weather formulas.

• Density altitude calculator

  How thin the air is for your engine and wings: pressure altitude, ISA deviation and density altitude.

• Crosswind component calculator

  The crosswind and headwind on a runway from the wind's direction and speed.

• True airspeed calculator

  True airspeed from calibrated airspeed, pressure altitude and temperature.

• Wind correction (E6B) calculator

  Heading to fly and ground speed for a course, given the wind.

• Time, speed and distance calculator

  Give two, leave one blank, and it solves for the third. Distance in nautical miles, speed in knots.

• Top of descent calculator

  How far out to start down, and the descent rate to hold it.

• Fuel and endurance calculator

  Endurance and range from fuel on board, burn rate, speed and a reserve.

• Weight and balance calculator

  Total weight and centre of gravity from what is on board. The starting numbers are an example, so put in your aircraft's own.

• Cloud base calculator

  Height of the cloud base from the temperature and dew point.

• Pressure converter

  Altimeter and barometer pressure: inches of mercury, hectopascals (millibars), millimetres of mercury and kilopascals. Fill in one.

• Temporary flight restrictions

  The FAA's active TFRs, nationwide or for one state, with links to each.

• METAR and TAF decoder

  Paste a METAR or TAF and read it in words, with its flight category.

• VFR weather minimums

  Minimum visibility and cloud clearance by airspace class.

• Dew point calculator

  The dew point from temperature and relative humidity, and whether fog or dew is likely.

• Heat index calculator

  How hot it feels once humidity is counted (the US National Weather Service formula).

• Wind chill calculator

  How cold it feels with the wind (the US National Weather Service formula).

• Lightning distance calculator

  How far away a lightning strike is from the seconds between the flash and the thunder.

• Beaufort wind scale

  The Beaufort force for a wind speed, and what the sea looks like.

Boats

Hull speed and anchoring.

• Hull speed calculator

  The speed a displacement hull can not easily pass, from its waterline length.

• Anchor scope calculator

  How much rode to let out: the depth plus the height of your bow above the water, times the scope.

Drones, RC and radio

Batteries, props, motors, radio links, antennas and a live satellite tracker.

• LiPo flight time calculator

  Flight time from the battery's capacity and your average current draw, and the C rating it needs.

• Battery pack calculator

  Voltage, capacity and energy of a pack built from cells in series and parallel (LiPo, Li-ion, LiFePO4).

• Prop pitch speed calculator

  The top speed a propeller can pull the model to, from its pitch and the motor's RPM.

• Motor KV and RPM calculator

  No-load RPM of a brushless motor from its KV rating and the battery voltage.

• Thrust-to-weight ratio calculator

  Thrust against weight for a drone or model. Above 1 it can hover; racing quads run 5 to 10.

• Radio link budget calculator

  Signal strength at the receiver over open air, and how far the link reaches, for an FPV video or control link.

• Fresnel zone calculator

  How much clear space a radio link needs around the straight line between the antennas.

• Antenna length calculator

  Dipole and vertical lengths for a frequency.

• dBm to watts converter

  Radio power in dBm, milliwatts and watts. Fill in dBm or milliwatts.

• Ohm's law calculator

  Volts, amps, ohms and watts: give any two, leave the others blank.

• LED resistor calculator

  The series resistor for an LED, and the nearest standard value.

• Satellite tracker

  Where the space station is right now, and when it passes over a place. Worked out in your browser.

PC building

Power supply, memory, monitors, storage and input-device tests.

• PSU wattage calculator

  How big a power supply a build needs, from the parts' own power draw.

• RAM latency calculator

  The true latency of a memory kit in nanoseconds, and its bandwidth: a CAS number means nothing without the speed.

• PPI and screen size calculator

  Pixel density, pixel size and physical dimensions of a screen.

• Monitor bandwidth calculator

  Whether a cable and port can carry a resolution and refresh rate, before compression.

• RAID calculator

  Usable space and fault tolerance for RAID 0, 1, 5, 6 and 10.

• File transfer time calculator

  How long a download, upload or copy takes.

• Drive capacity calculator

  Why a 1 TB drive shows less than 1 TB: drive makers count in powers of ten, operating systems in powers of two.

• Cost per terabyte calculator

  Compare storage by what a terabyte costs.

• Electricity cost calculator

  What a device costs to run: a PC, a server, a heater, a charger.

• UPS runtime calculator

  How long a battery backup carries a load.

• Gamepad tester

  Every button and stick of a connected controller, and drift.

• Mouse tester

  Click speed, double-click faults, polling rate, buttons and wheel.

• PC hardware, step by step

  CMOS battery, RAM, CPU and thermal paste, graphics card, M.2 and SATA drives, cables and first boot.

Photography and astronomy

Depth of field, exposure, field of view and telescope sums.

• Depth of field calculator

  How much of the picture is sharp: near and far limits and the hyperfocal distance for a lens, aperture and subject distance.

• Exposure value calculator

  Exposure value (EV) for an aperture, shutter speed and ISO, and the shutter speed that gives the same exposure at other apertures.

• Field of view calculator

  How wide a lens sees on a camera sensor: horizontal, vertical and diagonal angle.

• Telescope magnification calculator

  Magnification, exit pupil, limiting magnitude and field of view for a telescope and eyepiece.

Electronics

Resistor colours, dividers, time constants and the 555 timer.

• Resistor color code calculator

  The value of a four-band resistor from its colours.

• Voltage divider calculator

  The output of two resistors in series, and the current they draw.

• RC time constant calculator

  Time constant, cutoff frequency and charge times of a resistor and capacitor.

• 555 timer calculator

  Frequency and duty cycle of a 555 in astable mode.

Cars and engines

Tire sizes, gearing, displacement and trip costs.

• Tire size calculator

  Diameter and circumference of a tire, and how much a different size makes the speedometer read wrong.

• Speed from RPM and gearing calculator

  Road speed for an engine speed, tire size and overall gear ratio.

• Engine displacement calculator

  Displacement from bore, stroke and cylinders.

• Trip fuel cost calculator

  What a drive costs in fuel.

Running and lifting

Pace and race predictions, one-rep max and heart rate zones.

• Running pace calculator

  Pace and speed from a distance and a time, and what that pace predicts for other race distances.

• One-rep max calculator

  Your estimated best single from a set of several repetitions.

• Heart rate zones calculator

  Training zones from your age, and your resting heart rate if you know it.

Home, garden and 3D printing

Lumber, concrete, mulch, paint and filament.

• Board feet calculator

  Lumber volume in board feet.

• Concrete calculator

  Cubic yards of concrete for a slab, and how many bags of mix.

• Mulch and soil calculator

  Cubic yards of mulch, soil or gravel for a bed, and how many bags.

• Paint calculator

  Gallons of paint for a wall or room.

• 3D printer filament calculator

  Filament length for a weight, or weight for a length, by material and diameter.

Network and sysadmin

Subnets, cron, permissions, hashes, tokens and reference tables.

• Subnet calculator

  Network, mask, broadcast and hosts for an address and prefix, and how to split it.

• IPv6 address expander and compressor

  Expand or compress an IPv6 address.

• Cron expression explainer

  What a cron expression means and its next run times.

• Chmod calculator

  Tick permissions, get the octal and the command.

• Hash generator

  MD5, SHA-1, SHA-256, SHA-384, SHA-512 and CRC32 of text or a file, checked in your browser.

• JWT decoder

  Read a token's header, payload and expiry.

• HTTP status codes

  Every HTTP status code, filterable.

• Common network ports

  Well-known TCP and UDP port numbers.

• DNS record types

  A, AAAA, CNAME, MX, TXT and the rest, with examples.

• Regex tester

  Try a regular expression against text and see every match.

• JSON formatter

  Format, validate and minify JSON.

• Encoder and decoder

  URL, Base64 and HTML encoding and decoding.

• Text compare

  Compare two texts line by line.

• Unix timestamp converter

  Unix time to a date and back.

• Number base converter

  Binary, octal, decimal and hexadecimal, and text to binary.

Text and converters

Text tools, converters and generators.

• Word counter

  Words, characters, sentences and reading time.

• Case converter

  Upper, lower, title, sentence, camel, snake and kebab case.

• Lorem ipsum generator

  Placeholder text by the paragraph.

• Morse code translator

  Text to Morse and back, with sound.

• Roman numeral converter

  Numbers to Roman numerals and back.

• Unit converter

  Length, mass, volume, area, speed, temperature, time and data.

• Text to speech

  Read text aloud with your device's voices.

• QR code generator

  A QR code for any text or link, drawn in your browser.

• Color picker

  Pick a colour and copy it as hex, RGB or HSL.

• Online notepad

  A page to type on, kept in your browser.

Money, health and everyday

Loans, interest, health, dates, and small helpers.

• Calculator

  A scientific calculator.

• Graphing calculator

  Plot functions of x.

• BMI calculator

  Body mass index in metric or imperial.

• Age calculator

  Exact age from a birth date.

• Percentage calculator

  Percent of, percent change and percent difference.

• Tip calculator

  A tip and the bill split between people.

• Date calculator

  Days between two dates, or a date plus days.

• Calendar

  Any month or year.

• Pomodoro timer

  Focus and break intervals.

• Wheel spinner

  Spin a wheel of names or choices.

• Metronome

  A steady beat at any tempo.

• Tuner

  Tune a guitar, ukulele, bass or violin with the microphone.

• Coin flip

  Heads or tails.

• Dice roller

  Roll one or more dice.

• Random number generator

  A random number in a range.

• Password generator

  A strong password made in your browser.

• UUID generator

  A random UUID.

Tests for your devices

Camera, microphone, keyboard, speakers and screen.

• Webcam test

  See what your camera sees.

• Microphone test

  Check your microphone and its level.

• Keyboard test

  See every key you press light up.

• Speaker and headphone test

  Left, right and full-range test tones.

• Screen test

  Solid colours to find dead or stuck pixels.

• Your browser and screen

  Your screen size, browser and device.

• Ruler

  A ruler at real size, in inches or centimetres.

Games

Play in the page.

• Tic tac toe

  Against a computer that does not lose.

• Snake

  The classic.

• Minesweeper

  Three sizes.

• 2048

  Slide and merge tiles.

• Memory match

  Find the pairs.

• Sudoku

  Puzzles, hints, and a solver for one you are stuck on.

Money

• 50/30/20 budget calculator

  Take-home pay split into needs, wants and savings.

• Emergency fund calculator

  How much to keep for an emergency, and how long it takes to get there.

• Savings and bank interest calculator

  What a savings account, high-yield savings account or money market account grows to, from its APY or its APR.

• APR to APY converter

  The yearly rate with compounding (APY) from a nominal rate (APR), and back.

• CD calculator

  What a certificate of deposit is worth at maturity, and what breaking it early costs.

• Compound interest calculator

  Growth of savings with regular deposits.

• Rule of 72

  How many years money takes to double at a rate of return, by the rule and exactly.

• Retirement savings calculator

  What saving each month grows to by retirement, and the income it could pay by the 4% rule.

• Credit card payoff calculator

  How long a card balance takes to pay off at a monthly payment, what it costs, and the payment to clear it by a date.

• Debt snowball vs avalanche calculator

  Up to four debts paid with one monthly budget: smallest balance first (snowball) or highest rate first (avalanche).

• Loan calculator

  Payment and payoff schedule for any loan.

• Auto loan calculator

  Monthly payment on a car loan.

• Mortgage calculator

  Monthly payment and total interest.

• How much house can I afford

  The price your income supports by the 28/36 rule lenders start from, at today's rate.

• 1% rule calculator

  Whether a rental's monthly rent is at least 1% of what the property costs, and the rent it would take.

• Rental property calculator (cap rate and cash-on-cash)

  A rental's net operating income, cap rate, monthly cash flow and cash-on-cash return.

How things worked

• How to dial a rotary phone

  Lift the handset, turn the dial to the stop, and hear it click back.

• How to use a pay phone

  Coins in, dial, and the coin return when nobody answers.

• How to make change

  Ring up a sale, open the drawer, and count the change back.

• How a cassette tape works

  Play, fast-forward, flip to side B, and wind it back with a pencil.

• How to use a typewriter

  Type, hear the bell, and throw the carriage back.

• How to change a smoke alarm battery

  The low-battery chirp, the battery swap, and the monthly test.

• How to read an analog clock

  Turn the hands, read the time, and set the clock.

• How to write a check

  Fill in a practice check, and have it checked: words, numbers, signature.

• How to drive a stick shift

  Clutch, gas and gears, the bite point, and a stall when you get it wrong.

• How to use a fire extinguisher

  When to fight a fire and when to leave, and P.A.S.S.: pull, aim, squeeze, sweep.

• How to change a flat tire

  Loosen, jack, swap, lower, and tighten in a star, in the right order.

• How to shut off your water

  Find the main valve, close a gate or ball valve, and check at a faucet.

• Car checks anyone can do

  The oil dipstick, tire pressure, the penny tread test, and jumper cables in the right order.

Safety protocols

• Electrical safety

  Static inside a computer, and live-dead-live before touching household wiring.

• Eye protection by job

  Pick the job and the eyewear: glasses, goggles, face shield, welding or eclipse filters.

• Cleaning products not to mix

  Bleach with ammonia or acids, and what to do if it goes wrong.

• Mowing safely

  Clear the lawn, dress for it, and the clog, slope, child and refuelling rules.

• Safety on a plane

  Batteries, the belt, your nearest exit, your own mask first, brace, and leaving bags behind.