Engineering & construction
517 engineering and construction calculators: electrical circuits, mechanics, materials, structures and building quantities. Results with the formula and units in view, so you can check a design before you build it, free in your browser.
Ohm's law calculator
Give any two of voltage, current, resistance and power and the other two are worked out: 12 V at 2 A means 6 ohms and 24 watts.
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EV charge time calculator
Estimate how long a top-up takes: a 60 kWh battery charged from 20 to 80 percent on a 7.4 kW wallbox needs about 5.41 hours, drawing 40 kWh from the grid to add…
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Tire size calculator
A 205/55R16 tire has a 112.8 mm sidewall, a 631.9 mm overall diameter and turns 503.73 times per kilometre: type any metric tire code to get the same four…
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Resistor color code calculator
Enter the color bands from left to right and get the value: brown, black, red, gold is 1000 ohms with a 5 % tolerance.
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Voltage divider calculator
12 V across two 1000-ohm resistors gives 6 V at the midpoint, a ratio of 0.5 and an attenuation of −6.0205999133 dB: enter the input voltage, R₁ and R₂ to get…
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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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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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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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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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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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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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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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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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Antenna length calculator
Type a frequency and get the wavelength in vacuum with the quarter-wave and half-wave element lengths: 100 MHz gives about 3 m, 75 cm and 1.5 m.
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Battery runtime calculator
Divide the usable energy in watt-hours by the load power in watts to see how long a pack keeps a device running: 72 Wh into a 12 W load lasts 6 hours.
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Capacitor energy calculator
A 1000 µF capacitor charged to 12 V holds 0.072 J. Enter the capacitance in farads and the voltage in volts to get the stored energy; a negative voltage gives…
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Speaker crossover calculator
A 1 mH inductor with a 10 µF capacitor sets a crossover corner close to 1592 Hz. Enter the inductance in henries and the capacitance in farads to see where a…
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dBm to dBW calculator
A 30 dBm transmitter is 0 dBW, because dBm counts from one milliwatt and dBW from one watt, always 30 dB apart.
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dBm to watts calculator
A level of 30 dBm is exactly 1 W, or 1000 mW, and 0 dBm is one milliwatt. Enter a reading in dBm from an analyzer or a datasheet and get the linear power in…
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Electric potential calculator
One microcoulomb seen from 10 centimetres sits at roughly 9 × 10⁴ volts, counted from zero at infinity.
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EMF terminal voltage calculator
A 12 V cell with 0.5 Ω of internal resistance delivering 2 A shows 11 V at its terminals, because 1 V is lost inside.
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Inductor energy calculator
A 0.1 H coil carrying 2 A stores 0.2 J in its magnetic field. Enter the inductance and the current; a reversed current stores the same energy as a forward one…
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kWh calculator
A 1000 W load running for 2 hours uses 2 kWh, the unit printed on utility bills and appliance labels.
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Inverting amplifier calculator
Matched resistors give a gain of −1 and a ten-to-one feedback ratio gives −10: enter Rin and Rf and get the ideal closed-loop gain of an inverting amplifier…
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Electrical power calculator
12 volts at 2 amperes is 24 watts, and you also see the 6 Ω that pair implies. Enter any two of voltage, current and resistance to get the power and the missing…
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Parallel resistance calculator
Two 10 Ω resistors in parallel give 5 Ω, and three 100 Ω resistors give about 33.3 Ω. Enter the value of each branch to get the single equivalent resistance…
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RLC resonant frequency calculator
With 1 mH, 1 µF and 10 Ω, a series RLC circuit resonates at about 5 kHz with a Q of about 3. Enter the three values to get the resonant frequency, the angular…
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Smoothing capacitor calculator
A 1 A load on 50 Hz mains with 1 V of ripple needs 10 000 µF after a full-wave rectifier, because the ripple runs at 100 Hz.
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Solenoid magnetic field calculator
1000 turns per metre carrying 2 A produce about 2.513 mT inside a long ideal solenoid. Enter the turn density and the current to get the interior field in…
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Acceleration calculator
A speed gain of 20 m/s over 4 seconds is an average acceleration of 5 m/s²: enter the change in velocity and the time it took, and the calculator divides one by…
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Circular motion velocity calculator
A 2 m radius covered in a 4 s lap gives a speed of π m/s, or one circumference of 4π m every period.
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Free fall time calculator
Dropped from rest, an object falls 100 m in 4.5160075575 seconds under standard gravity of 9.80665 m/s².
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Friction force calculator
A coefficient of 0.3 and a normal force of 100 N give 30 N of friction: multiply the two to see how hard the surfaces resist sliding, with static or kinetic…
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Inelastic collision calculator
When a 2 kg cart at 3 m/s sticks to a 4 kg cart moving at −1 m/s, the pair moves on at 0.3333333333 m/s.
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Lever calculator
With a 2 m effort arm and a 0.5 m load arm, a push of 25 N balances a 100 N load, a mechanical advantage of 4.
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Gravitational potential energy calculator
Lift 2 kg by 5 m with g at 9.8 m/s² and it stores 98 J relative to where it started. Below the reference level the energy turns negative. Free in your browser.
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Projectile max height calculator
Launch at 20 m/s and 45 degrees and the projectile peaks 10.1971621298 m above the launch point after 1.4420964982 seconds, with no air resistance.
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RPM to linear speed calculator
A wheel of 0.25 m radius turning at 60 rpm makes one turn per second, so its rim covers a full circumference every second.
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Spring potential energy calculator
A spring of 200 N/m stretched 0.1 m stores 1 J of elastic energy. Enter the stiffness and the stretch or compression to get the stored energy; this is spring…
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Velocity components calculator
A speed of 10 m/s at 30° splits into 8.6602540378 m/s horizontally and 5 m/s vertically. Enter the speed and the angle from the horizontal to get both parts and…
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Weight calculator
A 70 kg mass under standard Earth gravity of 9.80665 m/s² weighs 686.4655 N. Enter the mass and the local g, such as about 1.62 m/s² for the Moon, to get weight…
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AWG ampacity calculator
Pick a wire gauge, an insulation class and copper or aluminum, and read the maximum safe continuous current: 12 AWG copper at 75 °C carries 25 A.
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AWG wire gauge calculator
Turn an AWG size into solid-copper diameter, cross-section and DC resistance: AWG 10 is about 2.59 mm across with 5.26 mm² of copper.
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Battery life calculator
Divide a cell's milliamp-hour rating by the device's average draw in milliamps to estimate runtime: a 3000 mAh phone cell at 150 mA lasts 20 hours.
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Capacitive reactance calculator
A 100 µF capacitor at 60 Hz presents about 26.5258238486 Ω, and the figure drops as frequency or capacitance rises.
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Capacitor charge calculator
A 1 µF capacitor held at 5 V stores 5 µC, and this calculator gives that product of capacitance and voltage in coulombs.
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Capacitor charging calculator
With 1 kΩ, 1 µF and a 5 V supply, the capacitor reaches 3.16060279414 V after 1 ms, which is one time constant and 63.2120558829% of the supply.
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Parallel capacitance calculator
Three capacitors of 10, 22 and 47 µF in parallel give 79 µF: the values simply add. Enter the list in one unit to check a decoupling bank on a power rail or a…
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Series capacitance calculator
Capacitors of 10, 20 and 47 µF in series come out a little under 6 µF, always below the smallest one.
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Electric charge calculator
A steady 2 A flowing for 5 seconds moves 10 coulombs. Enter any two of charge, current and time and the calculator finds the third, refusing negative durations…
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Coulomb's law calculator
Charges of 2 µC and -3 µC held 0.05 m apart attract each other with about twenty-one and a half newtons.
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Current divider calculator
A current of 10 A entering 100 Ω in parallel with 300 Ω splits into 7.5 A and 2.5 A, with the larger share through the smaller resistor.
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Electric field force calculator
A 2 microcoulomb charge in a 5000 N/C field feels 0.01 N. Enter charge and field with their signs, and the force comes out in newtons, pointing with the field…
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Electric field calculator
One microcoulomb seen from 10 centimetres gives a field of about 8.99 × 10⁵ N/C, and doubling the distance cuts it to a quarter.
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Electricity cost calculator
A 1500 W heater running for 2.5 hours uses 3.75 kWh; multiply by your rate per kilowatt-hour and you have the running cost of that session.
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Frequency period converter
A 50 Hz mains waveform repeats every 0.02 seconds, and a clock edge every microsecond means one megahertz.
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Inductive reactance calculator
A 0.1 H coil at 50 Hz opposes alternating current with about 31.416 Ω of reactance. Enter the frequency and the inductance to get the reactance in ohms and the…
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LC resonant frequency calculator
1 mH with 1 µF resonates at about 5033 Hz, roughly 5 kHz. Enter the inductance in henries and the capacitance in farads to get the natural frequency of an…
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LED resistor calculator
A 5 V supply, a 2 V LED and 0.02 A need a 150 Ω resistor dissipating 0.06 W, so a 0.125 W part is suggested.
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Magnetic field of a straight wire calculator
A current of 10 A produces 0.00004 T at 5 cm from a long straight wire: enter the current and the perpendicular distance and get the field strength from…
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