Electrical calculations are central to every electronics project, power system, and electrical installation. From decoding a resistor’s colour bands to sizing a solar array, these calculators cover the breadth of practical electrical engineering - referencing NEC, IEC, and AWG standards where relevant.

Six Electrical Engineering Calculators

Resistor Colour Code Calculator - Decodes 4-band and 5-band resistor values from colour band selection. Also works in reverse: enter a resistance value and get the correct colour band sequence. Uses the EIA standard colour code table.

Voltage Divider Calculator - V_out = V_in × R2 ÷ (R1 + R2). Enter any three values to find the fourth. Shows divider ratio and current draw. Used in sensor interfaces, ADC scaling, and BJT biasing. Pair with the Ohm’s Law Calculator for the full circuit picture.

Transformer Ratio Calculator - Three modes: find secondary voltage (V2 = V1 × N2/N1), find turns ratio for a required transformation, and find impedance transformation (Z2 = Z1 × (N2/N1)²). Used in power supply design, audio impedance matching, and mains isolation.

Wire Gauge Calculator - AWG lookup (diameter, area, resistance/metre, ampacity at 60/75/90°C insulation ratings) and voltage-drop calculation for any run length and current, with NEC 3% threshold warning.

Power Calculator - P = VI = I²R = V²/R. Enter any two of V, I, R, P to get the other two. The essential complement to the Ohm’s Law Calculator - use them together for complete circuit characterisation.

Solar Panel Output Calculator - Daily, monthly, and annual energy generation from panel capacity (Wp), peak sun hours, and system efficiency. Array sizing mode: enter daily consumption and PSH to find required panel capacity, battery storage (Ah), and estimated annual savings.

Practical Reference: Solar in India

India receives 4–7 peak sun hours daily (PSH) - Rajasthan/Gujarat at 5.5–7, northeastern states at 3.5–4.5. A 1 kWp system at 5 PSH with 80% efficiency generates ~4 kWh/day = 1,460 kWh/year. At ₹7/kWh savings ≈ ₹10,220/year. Use the Solar Panel Output Calculator with your local PSH for accurate sizing.

Frequently Asked Questions

How do I read a 5-band resistor colour code?

Bands 1–3 are the first three digits, band 4 is the multiplier, band 5 is tolerance. The Resistor Colour Code Calculator handles both 4-band and 5-band automatically.

What AWG wire should I use for a 20 A circuit?

12 AWG minimum per NEC Table 310.16 for 75°C insulation at 20 A. For longer runs, check voltage drop in the Wire Gauge Calculator - runs over 15 m at 20 A may need 10 AWG to stay within the 3% NEC guideline.

What is the difference between a step-up and step-down transformer?

Step-up increases voltage (N2 > N1) for power transmission. Step-down reduces voltage (N2 < N1) for domestic supply. Both are handled by the Transformer Ratio Calculator.

How many peak sun hours does my location receive?

Typical India values: Delhi 4.5–5.5, Mumbai 4.5–5.5, Jaipur 5.5–6.5, Kolkata 4.0–5.0. Use 5.0 as a conservative national average in the Solar Panel Output Calculator.