Low-Voltage Electronics & DIY
The everyday math of hobby electronics, worked out for you. Ohm's law in any direction, LED and parallel resistors, voltage dividers, battery runtime and charge time, and the power conversions that keep a low-voltage project running.
Available now
3 live
Available
Ohm's Law
Voltage, current, resistance, or power from any two known values.
AvailableLED Series Resistor
Resistor value, nearest standard, and power rating for LEDs in series.
AvailableParallel Resistor
Equivalent resistance of up to four parallel resistors.
All 35 calculators
linked tools are live; the rest are on the build list- Ohm's Law CalculatorVoltage, current, resistance, or power from any two known values.Live
- LED Series Resistor CalculatorResistor for one or more low-voltage LEDs in series.Live
- Parallel Resistor CalculatorEquivalent resistance for multiple parallel values.Live
- Voltage Divider CalculatorOutput voltage and resistor values for unloaded dividers.Soon
- Battery Runtime CalculatorRuntime from watt-hours, load, efficiency, and usable capacity.Soon
- Battery Charge Time CalculatorCharge time from capacity, current, and efficiency.Soon
- Watts, Volts & Amps CalculatorOne electrical quantity from the other two for DC systems.Soon
- mAh to Watt-Hours CalculatorConverts milliamp-hours and voltage into watt-hours and back.Soon
- Solar Battery Runtime CalculatorHow long a battery can support a DC load.Soon
- Battery Pack Series-Parallel CalculatorPack voltage, capacity, energy, and cell count.Soon
- Battery C-Rate CalculatorConverts current and capacity into charge or discharge C-rate.Soon
- Parallel LED Resistor CalculatorBranch resistors and total current for parallel LEDs.Soon
- Series Resistor CalculatorTotal resistance and voltage drop across series resistors.Soon
- DC Voltage Drop CalculatorLow-voltage cable drop from current, length, and conductor resistance.Soon
- Frequency & Wavelength CalculatorConverts signal frequency to wavelength for a propagation speed.Soon
- LED Strip Power Supply CalculatorSupply wattage from strip length and watts per meter.Soon
- LED Strip Voltage Drop EstimatorEstimates drop along a strip from current and feed layout.Soon
- Solar Panel Charging Time CalculatorBattery charge time from panel output and system efficiency.Soon
- RC Time Constant CalculatorCharge and discharge timing for resistor-capacitor circuits.Soon
- Capacitor Energy CalculatorStored energy from capacitance and voltage.Soon
- PWM Duty Cycle CalculatorOn-time, off-time, duty cycle, or average output.Soon
- 555 Timer CalculatorAstable frequency and duty cycle or monostable pulse duration.Soon
- Speaker Impedance CalculatorCombined impedance for series and parallel speaker wiring.Soon
- Resistor Color Code CalculatorDecodes or generates 3-, 4-, 5-, and 6-band resistor values.Soon
- Passive Crossover CalculatorFirst-order capacitor or inductor values for an impedance.Soon
- Capacitors in Series & Parallel CalculatorEquivalent capacitance for mixed networks.Soon
- SMD Resistor Code CalculatorDecodes 3-digit, 4-digit, and EIA-96 surface-mount markings.Soon
- Op-Amp Gain CalculatorInverting or non-inverting gain and resistor ratios.Soon
- Capacitive Reactance CalculatorReactance from capacitance and frequency.Soon
- ADC Resolution CalculatorVolts per step and digital code from reference and bit depth.Soon
- Inductive Reactance CalculatorReactance from inductance and frequency.Soon
- Stepper Motor Steps-per-Millimeter CalculatorSteps from microstepping, gearing, and lead screw.Soon
- USB Power Budget CalculatorTotals device current against a USB supply budget.Soon
- DAC Output Voltage CalculatorAnalog output from digital code, resolution, and reference.Soon
- Motor Torque-to-Linear-Force CalculatorConverts torque to ideal belt, pulley, or lead-screw force.Soon
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