Electrical Calculator
Stateless. Precise. Private.
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About the Utility
The Electrical Calculator is a fast, accurate, and completely client-side web utility that provides ten essential high-demand electrical calculations with results rounded to exactly five decimal places.
Designed for electricians, electronics engineers, students, hobbyists, and technicians, this tool delivers instant, reliable answers for DC power, AC single-phase and three-phase power, all variations of Ohm’s Law, power dissipation in resistors, capacitor energy storage, and resonant frequency of LC circuits.
Every calculation runs entirely in your browser. There is no server, no tracking, no data collection, and no account required. The application is fully static and works offline once loaded, making it perfect for field work, classroom use, or anywhere internet access is limited or unavailable.
Precision is at the core of the design. All results are computed with full floating-point accuracy and then rounded to exactly five decimal places. This level of detail helps eliminate rounding errors when values are used in further calculations, ensuring professional-grade reliability.
The clean, responsive interface features a single dropdown to select any of the ten calculations. Input fields adapt automatically, never exceeding five inputs, and results update in real time as you type. The tool uses Bootstrap for a modern, mobile-friendly layout.
Built with SvelteKit and deployed as a static site on GitHub Pages, the Electrical Calculator prioritizes speed, simplicity, and privacy. It contains no external dependencies beyond Bootstrap and requires no installation. Simply open the page and start calculating with confidence.
Calculations We Cover
Ten practical, frequently used electrical formulas — all computed with extreme accuracy to five decimal places.
1. DC Power P = V × I
The DC Power formula calculates the electrical power in watts when voltage and current are known. This is one of the most fundamental calculations used in battery systems, solar installations, automotive electronics, and low-voltage circuit design. Our calculator instantly multiplies voltage by current and displays the result with five decimal places for maximum precision.
Accurate power values help determine wire gauge requirements, fuse ratings, heat dissipation, and overall system efficiency. Small rounding errors in power calculations can lead to significant differences when scaling up to larger systems. The five-decimal precision ensures your results remain reliable for further engineering work.
Simply enter voltage in volts and current in amperes. The result updates live as you type, allowing quick comparison of different operating conditions. Ideal for students learning basic electrical relationships and professionals verifying load requirements in the field.
2. AC Single-Phase P = V × I × PF
Single-phase AC power calculation includes the power factor to determine true power delivered to the load. This formula is widely used for household appliances, lighting circuits, and small motors. The calculator multiplies voltage, current, and power factor, then rounds the result to five decimal places.
Power factor accounts for the phase difference between voltage and current. A lower power factor means more current is required to deliver the same useful power, increasing energy costs and heat in cables. Testing different power factor values helps optimize system efficiency.
Enter voltage, current, and power factor (between 0 and 1). The tool provides instant feedback, making it easy to see how power factor affects real power consumption. Essential for electricians sizing circuits and engineers designing efficient AC systems.
3. Three-Phase Power P = √3 × V × I × PF
Three-phase power is the standard for industrial motors, heavy machinery, and large commercial installations. The formula includes the square root of three because power is distributed across three phases. Our calculator handles the complex math internally and delivers the final result with five-decimal precision.
Accurate three-phase calculations are critical for correct cable sizing, transformer selection, and protective device ratings. Even small errors can lead to overheating or inefficient operation.
Input line voltage, line current, and power factor. The result updates instantly, allowing rapid comparison between different loads or power factors. Perfect for factory maintenance teams and electrical design engineers.
4. Ohm’s Law – Voltage V = I × R
This variation of Ohm’s Law calculates voltage when current and resistance are known. It is commonly used when verifying power supply output or checking voltage drop across components.
Precise voltage calculations help ensure devices receive the correct operating voltage and prevent damage from over or under-voltage conditions. The five-decimal output maintains accuracy when these values are used in further calculations.
Enter current in amperes and resistance in ohms. The calculator instantly shows the voltage in volts. Real-time updating makes it easy to test different scenarios and understand the direct relationship between current, resistance, and voltage.
5. Ohm’s Law – Current I = V / R
Calculate current flowing through a circuit when voltage and resistance are known. This is essential for determining how much current a device will draw or for sizing fuses and circuit breakers correctly.
The calculator includes protection against division by zero and clearly displays an error message if resistance is entered as zero. Results are shown with five decimal places for high precision in sensitive electronic circuits.
Enter voltage and resistance. The result updates live, helping students visualize how resistance affects current flow and assisting technicians during troubleshooting.
6. Ohm’s Law – Resistance R = V / I
Determine resistance when voltage and current are measured. This mode is frequently used when verifying component values or diagnosing faulty resistors and loads.
Accurate resistance calculation helps identify open circuits, short circuits, or degraded components. The tool prevents division by zero when current is zero and provides clear feedback.
Input voltage and current to receive resistance in ohms with five decimal places. The real-time display makes it simple to compare measured values against expected specifications.
7. Resistance Power (I) P = I² × R
Calculate power dissipated as heat in a resistor when current and resistance are known. This formula is vital for selecting the correct wattage rating of resistors to prevent overheating.
Because power is proportional to the square of the current, small increases in current cause large increases in heat. The calculator’s five-decimal precision helps you make safe design decisions and properly size heatsinks when needed.
Enter current and resistance. Results update instantly, allowing quick testing of different operating conditions and ensuring components stay within safe thermal limits.
8. Resistance Power (V) P = V² / R
This formula calculates power dissipation when voltage across the resistor and resistance value are known. It is especially useful when current is difficult to measure directly.
The voltage-squared relationship means power increases dramatically with higher voltages. Accurate calculation prevents using underrated resistors that could fail under load.
Enter voltage and resistance. The tool displays power in watts with five decimal places and protects against division by zero. Ideal for bench testing and circuit verification.
9. Capacitor Energy E = ½ × C × V²
Calculate the energy stored in a capacitor using capacitance and voltage. This is important for power supply design, backup systems, camera flashes, and pulsed circuits.
Because energy depends on the square of voltage, doubling the voltage quadruples the stored energy. The calculator shows results in joules with five decimal places, helping determine discharge times and safe handling procedures.
Enter capacitance in farads and voltage in volts. Real-time results make it easy to compare different capacitor and voltage combinations for optimal energy storage.
10. Resonant Frequency f = 1 / (2π√(L×C))
Compute the resonant frequency of an inductor-capacitor circuit. This formula is essential for radio frequency design, filters, oscillators, and tuned circuits.
Precise frequency calculation ensures circuits operate at the intended frequency. Even small deviations can cause poor performance. The calculator delivers the result in hertz with five decimal places for high accuracy.
Enter inductance in henries and capacitance in farads. The tool checks for positive values and updates the frequency instantly as you adjust component values.
Need more depth? Explore examples and applications in the Blog section.
How to Use the Electrical Calculator
Using the Electrical Calculator is intentionally simple and fast. The entire process takes just a few seconds and requires no prior setup or technical knowledge.
Select a Calculation
Choose from the dropdown menu at the top of the page. Ten essential electrical formulas are available, covering power, Ohm’s Law, resistance-based power, capacitor energy, and resonant frequency.
Enter the Required Values
The input fields will automatically adapt to the selected formula. Enter the numerical values using appropriate units (volts, amperes, ohms, farads, henries, etc.). You will never need more than five inputs.
View Instant Results
The result appears immediately below the inputs and updates in real time as you type. Every answer is displayed with exactly five decimal places for maximum precision and professional reliability.
The calculator handles edge cases gracefully, such as division by zero, and provides clear feedback when inputs are invalid. All calculations are performed locally in your browser with full floating-point precision before final rounding.