Free Online Electricity Calculators
Calculate electricity costs, UPS runtime, battery charging time, power, voltage, and current online — for free.
⚠️ Important Information and Safety
All VoltCalc calculator results are for informational purposes only and are estimates. They do not guarantee actual equipment performance, constitute professional technical advice, or provide instructions for installing or connecting devices. Before using the results in practice, independently verify them, check equipment specifications, and follow manufacturers' recommendations. Electrical work should be performed by qualified professionals. The website owner does not guarantee absolute calculation accuracy. Users' rights and the owner's liability under applicable law remain unaffected.
Electricity Cost
Calculate the energy consumption of household appliances and electricity costs per day, month, year, or any selected period based on the price per 1 kWh.
UPS Runtime
The UPS runtime calculator estimates how many hours a battery can power a router, computer, or other devices. The calculation takes into account battery voltage, capacity and type, load power, and system efficiency.
The result is an estimate, not a guaranteed backup runtime. The calculator uses approximate usable-capacity factors for different battery types. These are not universal discharge limits. Actual available capacity depends on the battery model, BMS, temperature, battery condition, load, and UPS cutoff voltage. For a more accurate estimate, check the battery and UPS manufacturer's specifications.
This calculation is an estimate. Actual runtime depends on temperature, battery age and condition, usable capacity, and UPS characteristics. For lead-acid batteries, the 50% factor is an approximation, not a guaranteed discharge limit.
Battery Charging Time
The battery charging time calculator estimates how many hours are needed to charge a battery. The calculation takes into account battery capacity, charger current, battery type, and a time allowance factor.
The result is an estimate. The calculator uses approximate factors for different battery types, which are not universal charging standards. Actual charging time depends on the charger's algorithm, temperature, battery condition, initial charge level, and current reduction near the end of charging. Follow the battery manufacturer's recommendations and use a compatible charger.
Power, Voltage and Current
The power, voltage, and current calculator helps you find an unknown electrical value using the formula P = U × I. Enter two known values — power, voltage, or current — to calculate the third.
The formula P = U × I is simplified and suitable for calculations in direct current (DC) circuits and simple loads. For alternating current (AC), active power may depend on the power factor and other electrical system parameters.
💡 How to use the calculator:
• To calculate power: P = U × I
• To calculate voltage: U = P ÷ I
• To calculate current: I = P ÷ U
Enter exactly two values and leave the third field empty. All values must be greater than zero.
Free VoltCalc Online Calculators
VoltCalc is a collection of simple online tools for everyday electrical calculations. Calculate electricity consumption costs, UPS backup runtime, battery charging time, and electrical power. All calculators are free and require no registration.
Frequently Asked Questions
Are VoltCalc calculators free?
Yes. All VoltCalc online calculators are free and require no registration. You can use them directly in your browser.
How do I calculate electricity costs?
Enter the appliance power in watts, operating hours per day, number of days, and the price per 1 kWh. The calculator will estimate energy consumption and its cost for the selected period.
How do I calculate UPS runtime from a battery?
Enter the battery voltage and capacity, battery type, power consumption of the connected devices, and system efficiency. The calculator will estimate the UPS backup runtime.
How do I calculate battery charging time?
Enter the battery capacity, charger current, battery type, and time allowance factor. The result will show the estimated charging time.
Are the calculator results accurate?
All VoltCalc results are estimates. Accuracy depends on the data entered, equipment specifications, and operating conditions. The calculators use simplified mathematical models and do not account for every characteristic of real electrical systems. Before using the results in practice, verify them against the equipment manufacturer's documentation.
How do I calculate power, voltage, or current?
Use the calculator based on the formula P = U × I. Enter two known values — voltage, current, or power — and the calculator will determine the third.