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.
Pendulum bob maximum speed calculator from length and angle
Release a 2 m pendulum at 30 degrees from the vertical and get the speed of the bob at the bottom of its swing, plus how far it drops on the way.
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Oscillator quality factor calculator
A resonance at 1200 Hz with a 30 Hz half-power bandwidth has a quality factor of 40. Enter both values in the same unit and get Q, the single figure that tells…
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Springs in parallel calculator
Three parallel springs of 120, 180 and 300 N/m act like a single spring of 600 N/m. List each stiffness and get the combined value and the number of springs…
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Archimedes principle calculator
Water at 1000 kg/m³ displaced by 0.002 m³ under 9.81 m/s² pushes up with 19.62 N: the calculator multiplies density, volume and gravity following Archimedes'…
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Simply supported beam center load calculator
A 1000 N load at the middle of a 6 m beam puts 500 N on each support and a maximum bending moment of 1500 N·m under the load.
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Will It Float Calculator
An object of 750 kg/m³ in water of 1000 kg/m³ floats, with a density ratio of 0.75: compare any object with any fluid and get a clear verdict, the signed…
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Gear train mechanical advantage calculator
Two stages of 20 to 60 and 15 to 45 teeth give a 9:1 ideal torque ratio, with the output turning the same way as the input: enter each mesh in order and see…
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Gravitational force comparison
Masses of 10 and 20 at a distance of 2 pull 16 times harder than masses of 5 and 10 at a distance of 4: enter two setups and see which attracts more strongly…
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Hydraulic lift calculator
Pistons of 2 and 10 cm turn a 100 N push into 2,500 N, because the force grows with the square of the diameter ratio.
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Manometer pressure calculator
A water column difference of 0.25 m under 9.81 m/s² means a pressure difference of 2452.5 Pa between the two ports.
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Pendulum energy calculator
Pick any point of the swing and see where the energy sits: a 0.5 kg bob on a 1 m string released at 30 degrees already carries most of it as motion by 15…
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Projectile time at height calculator
A ball launched at 20 m/s and 60° passes 10 m twice, once on the way up and once on the way down; this calculator gives both moments and the highest point it…
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Tipping angle stability
An object with a 0.4 m base and its centre of gravity 0.8 m high tips over at 14.0362434679°. Enter the base width and the centre of gravity height to see how…
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Torsional pendulum period
A body with a moment of inertia of 0.05 kg·m² on a wire of 0.2 N·m/rad swings with a period of 3.14159265359 s.
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Two-member bracket force calculator
With a 1000 N load and members at 30° and 120°, the first carries 500 N and the second 866.025404 N, both in tension.
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Power from current and resistance
Two amperes through 10 Ω dissipate 40 watts of heat. Enter the current and the resistance to get the power the resistor turns into heat, plus the voltage across…
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Resistance from power and voltage calculator
A load using 60 W at 120 V has an operating resistance of 240 Ω. Enter the voltage and the real power from a label or a measurement to get the ohms when an…
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Voltage drop percentage calculator
120 V at the source and 115.8 V at the load mean a 4.2 V drop, or 3.5 %, which fails the default 3 % limit.
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Voltage from power and current calculator
A heater drawing 1500 W at 12.5 A runs on 120 V: enter the watts and amps you measured and get the voltage, worked out as power divided by current.
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Charge from current and time calculator
A current of 2 A flowing for 5 seconds moves 10 coulombs: charge is simply current times time. Enter the current in amperes and the elapsed time in seconds to…
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Kirchhoff voltage law calculator
A 12 V source feeding a 5 V drop and one unknown drop leaves 7 V for the unknown. List the voltages around one closed loop, tag each as rise or drop, leave one…
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Norton equivalent calculator
A 12 V source behind 6 Ω becomes a 2 A current source with 6 Ω in parallel. Enter the source voltage and series resistance to get the Norton current, sign…
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Resistor power dissipation calculator
A 100 Ω resistor carrying 100 mA turns 1 W into heat, so with the default safety margin you should fit a 2 W part.
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EIA-96 SMD resistor code calculator
An SMD resistor marked 25C is 17.8 kΩ: the 25 points to 178 in the 96-row E96 table and the C multiplies by one hundred.
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Two resistor parallel calculator
1000 Ω in parallel with 2200 Ω gives 687.5 Ω: the product divided by the sum. Enter two resistances in ohms and get the equivalent, which always comes out lower…
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Voltage divider resistor calculator
Going from 12 V down to 5 V with 10000 Ω on top, the lower resistor must be 7142.85714286 Ω. Enter the input voltage, the target output and the upper resistor…
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Capacitance to capacitor code calculator
A 100 nF capacitor is marked 104, ten followed by four zeros in picofarads. Type a value with its unit to get the three-digit code and how it reads; values the…
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NTC thermistor beta resistance calculator
A 10 kΩ NTC with a beta of 3950 K, rated at 25 °C, drops below 4 kΩ at 50 °C. Enter the nominal resistance, beta and the temperature you need to get the…
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Pull-up resistor current calculator
A 10 kΩ pull-up on a 5 V supply draws 0.5 mA whenever the line is held low, and the resistor dissipates 0.0025 W.
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Five-band resistor color code calculator
Brown-black-black-red-brown reads as 10 kΩ with ±1 % tolerance, so the part may measure anywhere from 9,900 to 10,100 Ω.
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Resistor tolerance range calculator
A 1000 Ω resistor at ±5 % may measure anywhere from 950 to 1050 Ω, a ±50 Ω band and a 100 Ω span. Enter the nominal value and tolerance to get the limits for…
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Two capacitor series calculator
10 and 20 in series give about 6.6667 in the same unit: the product, 200, divided by the sum, 30. Enter two capacitor values and get the equivalent with each…
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Capacitive voltage divider
10 V across two equal 1 nF capacitors leaves 5 V on the lower one, a ratio of 0.5 and about −6 dB.
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Capacitor ESR power loss calculator
With 2.5 A of RMS ripple through 0.03 Ω of ESR, a capacitor turns 0.1875 W into heat, or 675 J every hour.
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Capacitor dielectric field strength calculator
With 1200 V across 0.5 mm, the field is 2.4 kilovolts per millimeter, only 24 % of a 10 kilovolt-per-millimeter dielectric, leaving 3800 V of headroom up to…
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RC charging voltage at time calculator
With 1 kΩ, 1 µF and a 5 V supply, the capacitor reaches about 63.2 % of the supply after 1 ms, exactly one time constant.
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RC snubber design calculator
A 24 V relay cutting 2 A through a 1 mH coil needs a 12 Ω resistor and a matching capacitor across the contact to absorb the 2 mJ released at switch-off.
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Series capacitor voltage sharing calculator
Across 400 V, a string of 100, 220 and 100 µF capacitors leaves the 220 µF part with the smallest share, and every part stays within its rating.
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AC real power calculator
Multiply RMS voltage, RMS current and power factor to get the real power an AC load turns into work: 230 V at 10 A with a power factor of 0.85 gives 1,955 W out…
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Air core solenoid inductance calculator
Estimate a single-layer air-core coil with L = μ₀N²A/l: doubling the turns makes the inductance four times larger, while doubling the coil length halves it.
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Coupling coefficient calculator
Coils of 10 mH and 40 mH sharing 6 mH of mutual inductance have a coupling coefficient of 0.3, or 30 %.
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Series RLC impedance calculator
100 Ω, 0.1 H and 1 µF in series at 1000 Hz behave inductively, because the coil's reactance outweighs the capacitor's.
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Inductance from reactance calculator
A reactance of 31.416 Ω at 50 Hz calls for a coil of about 0.1 H. Enter the ohms your design needs and the signal frequency, and the calculator divides by two…
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Inductor current ripple calculator
With 12 V across a 0.0001 H inductor, a duty cycle of 0.4 and 100 kHz switching, the current swings 0.48 A peak to peak.
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RF choke impedance calculator
At 100 MHz, a 1 µH choke presents 628.318530718 Ω to the RF signal, which counts as moderate blocking.
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Sine average voltage calculator
A sine wave of 10 V peak has an average rectified value of about 6.366 V, two over pi times the peak.
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VRMS from peak voltage calculator
A 170 V peak sine wave equals about 120.2 V RMS: enter the peak voltage and get the RMS value by dividing by the square root of two, plus the crest factor and…
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Series RL impedance calculator
A 100 Ω resistor in series with 0.1 H at 50 Hz gives about 104.8 Ω of impedance, with current lagging by about 17.4°.
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Line to phase voltage calculator
A 400 V three-phase supply gives loads about 230 V from line to neutral: enter either the line or the phase voltage of a balanced wye system and get the other…
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Phase shift to time delay calculator
At 1000 Hz, a 90° phase shift is a delay of 0.00025 seconds, one quarter of the period. Convert either way between degrees and seconds for any signal frequency…
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RLC resonance Q factor calculator
A series RLC circuit with 10 Ω, 10 mH and 1 µF has a Q of 10 and resonates at 10000 rad/s. Enter resistance, inductance and capacitance to see how sharply a…
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Shockley diode equation calculator
At 0.6 V, with a saturation current of 1 pA and a thermal voltage of 25.85 mV, the Shockley equation gives about 12 mA through an ideal diode.
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BJT Voltage Divider Bias Calculator
Find the operating point of a common-emitter NPN stage with divider bias: with 12 V, a 47 kΩ and 10 kΩ divider and a beta of 100, the base sits at about 2 V…
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Full-wave rectifier output calculator
A 12 V half-winding peak minus one 0.7 V diode drop gives 11.3 V peak at the load and a DC average of 7.193803 V.
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Impedance from R and X calculator
Resistance 3 Ω and reactance 4 Ω give an impedance of 5 Ω, plus its phase angle in degrees and radians.
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LED series string calculator
On a 12 V rail, three 3.2 V LEDs at 20 mA fit in one string with a 120 Ω resistor: enter supply, LED voltage and current to get the maximum count, the resistor…
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Linear regulator power calculator
Stepping 12 V down to 5 V at 0.5 A turns 3.5 W into heat: enter input, output and load current to see the regulator's dissipation, the power that reaches the…
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Zener diode power calculator
A 5.1 V Zener carrying 20 mA dissipates 0.102 W, which is 20.4 % of a 0.5 W rating. Enter the Zener voltage, its current in amperes and the data-sheet rating to…
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Aliasing frequency calculator
Find where a sampled tone really shows up: a 1,000 Hz tone sampled at 800 Hz has a Nyquist limit of 400 Hz and appears at 200 Hz.
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Battery C rate calculator
Convert between C rate and current for any battery: a 100 Ah battery at 0.5C means 50 A and an ideal two hours.
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