watts to volts

When you know how much power a device consumes and how much current it draws, the voltage is the ratio: V = P/I. A 60 W bulb drawing 0.5 A needs 120 V; a 100 W USB-C laptop charger delivering 5 A runs at 20 V. Solar panels are rated in watts, and matching them to a battery's voltage uses this exact division.

By EnginStack Editorial Team | Reviewed against NIST, BIPM and primary-source documentation About →
watts
amps
— volts
— —

Verified against NIST Special Publication 811 and BIPM SI definitions. The conversion factor is exact and traceable to the 1959 treaty constants.

watts to volts

The reverse of volts-times-amps is power-divided-by-amps, and it answers a different class of question: what voltage does this load need? USB-C's power delivery negotiates voltages from 5 V to 48 V to keep current low at high power; solar panels are speced in watts but must match a system voltage; and a device's label giving both watts and amps lets you compute its voltage directly. The formula is exact, and the only real-world complication is power factor on AC reactive loads.

volts = watts ÷ amps
V = P/I
Exact watt's law — the ratio of the power and current you provide.

Common watts to volts Values

wattsampsvoltsContext
60 W0.5 A120 VIncandescent bulb.
100 W5 A20 VUSB-C laptop charger.
1,800 W15 A120 VSpace heater.
300 W6.25 A48 VSolar panel into battery system.
120 W10 A12 VAutomotive accessory.

Engineering Context

Watts-to-volts completes the four-way watt/Ohm family with volts to watts, volts to amps, and amps to volts. The solar and charger angle connects to the energy hub's Wh to kWh — battery capacity is rated in watt-hours, which is this wattage times hours. The electric hub collects the full family.

More: V to W · W to A · A to V · Electric Hub

Related Unit Converters

Volts To Watts Watts To Amps Amps To Volts Electric Converters

Frequently Asked Questions

How do I convert watts to volts?

Divide watts by amps: V = P/I. A 60 W device drawing 0.5 A operates at 120 V. If you know resistance instead, V = √(P·R).

Why does USB-C use 20 volts for laptops?

To keep current manageable at high power. 100 W at 5 V would need 20 A — a thick, hot cable. At 20 V, the same 100 W needs only 5 A. That is V = P/I applied by the charger.

What voltage is a solar panel's watts rating?

A solar panel's wattage is rated at its maximum power point, which is a specific voltage–current pair (often around 30–40 V for a 300–400 W residential panel). Matching it to a battery bank voltage is exactly this calculation.