Enter any two values to calculate the others using Ohm's Law (Voltage, Current, Resistance, or Power).
Energy Consumption & Cost (Optional)
Calculation Results:
function calculateElectrical() {
var v = parseFloat(document.getElementById('elec_volts').value);
var i = parseFloat(document.getElementById('elec_amps').value);
var r = parseFloat(document.getElementById('elec_ohms').value);
var p = parseFloat(document.getElementById('elec_watts').value);
var h = parseFloat(document.getElementById('elec_hours').value);
var rate = parseFloat(document.getElementById('elec_rate').value);
var count = 0;
if (!isNaN(v)) count++;
if (!isNaN(i)) count++;
if (!isNaN(r)) count++;
if (!isNaN(p)) count++;
if (count < 2) {
alert("Please enter at least TWO values (Voltage, Current, Resistance, or Power) to perform Ohm's Law calculations.");
return;
}
// Perform Ohm's Law Calculations based on available pairs
for (var loop = 0; loop < 2; loop++) { // Loop twice to ensure all interdependent values fill
if (!isNaN(v) && !isNaN(i)) {
if (isNaN(r)) r = v / i;
if (isNaN(p)) p = v * i;
}
if (!isNaN(v) && !isNaN(r)) {
if (isNaN(i)) i = v / r;
if (isNaN(p)) p = (v * v) / r;
}
if (!isNaN(v) && !isNaN(p)) {
if (isNaN(i)) i = p / v;
if (isNaN(r)) r = (v * v) / p;
}
if (!isNaN(i) && !isNaN(r)) {
if (isNaN(v)) v = i * r;
if (isNaN(p)) p = (i * i) * r;
}
if (!isNaN(i) && !isNaN(p)) {
if (isNaN(v)) v = p / i;
if (isNaN(r)) r = p / (i * i);
}
if (!isNaN(r) && !isNaN(p)) {
if (isNaN(v)) v = Math.sqrt(p * r);
if (isNaN(i)) i = Math.sqrt(p / r);
}
}
// Display Values
document.getElementById('elec_volts').value = v.toFixed(2);
document.getElementById('elec_amps').value = i.toFixed(2);
document.getElementById('elec_ohms').value = r.toFixed(2);
document.getElementById('elec_watts').value = p.toFixed(2);
var mainHtml = "Voltage: " + v.toFixed(2) + " V" +
"Current: " + i.toFixed(2) + " A" +
"Resistance: " + r.toFixed(2) + " Ω" +
"Power: " + p.toFixed(2) + " Watts";
document.getElementById('elec_main_results').innerHTML = mainHtml;
// Calculate Energy Cost if data exists
if (!isNaN(p) && !isNaN(h)) {
var dailyKwh = (p * h) / 1000;
var costHtml = "Daily Consumption: " + dailyKwh.toFixed(3) + " kWh";
if (!isNaN(rate)) {
var dailyCost = dailyKwh * rate;
costHtml += "Daily Cost: $" + dailyCost.toFixed(2) + "";
costHtml += "Monthly Cost (30 days): $" + (dailyCost * 30).toFixed(2) + "";
costHtml += "Yearly Cost: $" + (dailyCost * 365).toFixed(2);
}
document.getElementById('elec_cost_results').innerHTML = costHtml;
document.getElementById('elec_cost_results').style.display = "block";
} else {
document.getElementById('elec_cost_results').style.display = "none";
}
document.getElementById('elec_result_box').style.display = "block";
}
function resetElectrical() {
document.getElementById('elec_volts').value = ";
document.getElementById('elec_amps').value = ";
document.getElementById('elec_ohms').value = ";
document.getElementById('elec_watts').value = ";
document.getElementById('elec_hours').value = ";
document.getElementById('elec_rate').value = ";
document.getElementById('elec_result_box').style.display = "none";
}
Understanding Electrical Calculations: Ohm's Law & Power
Whether you are a DIY enthusiast, a student, or a professional electrician, understanding the relationship between voltage, current, resistance, and power is fundamental. Our electrical calculator uses Ohm's Law and the Power Law to help you determine missing electrical values and estimate energy costs.
1. The Core Formulas (Ohm's Law)
Ohm's Law defines the relationship between Voltage (V), Current (I), and Resistance (R). The primary formula is:
Voltage (V) = I × R (Current multiplied by Resistance)
Current (I) = V / R (Voltage divided by Resistance)
Resistance (R) = V / I (Voltage divided by Current)
2. Electric Power (Watt's Law)
Power (P), measured in Watts, is the rate at which electrical energy is transferred. It is calculated using:
Power (P) = V × I (Voltage multiplied by Current)
Power (P) = I² × R (Current squared multiplied by Resistance)
Power (P) = V² / R (Voltage squared divided by Resistance)
3. Estimating Energy Consumption and Cost
To find out how much an appliance costs to run, you need to know its power rating (Watts) and how long it operates. The formula for energy in kilowatt-hours (kWh) is:
kWh = (Watts × Hours) / 1,000
Once you have the kWh, simply multiply it by your utility provider's rate (e.g., $0.12 per kWh) to find the total operating cost.
Practical Example
Suppose you have a space heater rated at 1,500 Watts running on a standard 120 Volt circuit.
Calculate Current: 1,500W / 120V = 12.5 Amps.
Calculate Resistance: 120V / 12.5A = 9.6 Ohms.
Daily Cost: If run for 5 hours a day at $0.15/kWh:
(1,500W * 5h) / 1000 = 7.5 kWh.
7.5 kWh * $0.15 = $1.13 per day.
Safety Warning
Always ensure that the current (Amps) does not exceed the rating of your circuit breaker or wiring. Overloading a circuit can lead to heat buildup and potential fire hazards. When in doubt, always consult a licensed electrician for residential or commercial wiring projects.