Electronics Calculators
Practical tools for circuit design, component selection and bench work. Instant results — no account, no ads, no friction.
Core calculators
What each tool does
| Calculator | What you solve |
|---|---|
| Ohm's Law | Any two of V, I, R, P known → calculates the remaining two. All six formula paths. |
| Watts / Volts / Amps | DC, single-phase AC and three-phase AC power. Includes power factor. |
| Voltage Divider | Vin + R1 + R2 → Vout, divider current, R1 voltage and resistor power. |
| LED Resistor | Supply voltage + LED Vf + current → required resistor value (with E12 nearest standard) and power dissipation. |
| Resistor Color Code | 4-band and 5-band resistor decoder. Color bands → resistance value and tolerance. |
| Capacitor Code | 3-digit SMD/ceramic capacitor code → pF / nF / µF. Unit converter included. |
| Voltage Drop | Wire length + gauge (AWG or mm²) + current → voltage drop and power loss. |
| Battery Life | Capacity (mAh) + load current → runtime in hours and minutes with efficiency factor. |
When to use these tools
- Before soldering — verify resistor value, power rating and LED current
- Bench setup — confirm supply voltage and current headroom for a load
- Cable sizing — check voltage drop on long DC runs (LED strips, solar, automotive)
- Battery projects — estimate runtime before committing to a pack size
- Component identification — decode resistor bands and capacitor codes from the part bin
Frequently Asked Questions
Do these calculators work for both DC and AC circuits?
Most tools target DC or low-frequency electronics. The Ohm's Law and Voltage Divider calculators assume resistive (DC) behaviour. The Watts/Volts/Amps tool explicitly covers DC, single-phase AC and three-phase AC with power factor. For RF or high-frequency work involving impedance, reactance and phase angle, use a dedicated RF calculator — these tools do not model parasitic capacitance or inductance.
Are the results accurate enough for real circuits?
Yes, for the intended purpose: planning and sanity-checking before measurement. Ohm's Law, power dissipation and voltage division are exact formulas with no approximation in these calculators. What varies in practice are component tolerances (resistors ±1–5%, capacitors ±10–20%), temperature drift, and parasitic effects in the physical layout. Use these tools to catch obvious errors — then measure the real circuit with a multimeter.
What is the E12 resistor series shown in the LED calculator?
E12 is a standard series of 12 preferred resistor values per decade: 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 Ω (and ×10 multiples). These are the values you find on the shelf at component suppliers. The calculator rounds your exact result to the nearest E12 value — always check whether rounding up or down keeps current within safe limits.