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Voltage divider calculator

Compute the output voltage of a two-resistor voltage divider.

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Enter Input voltage (V), R1 (Ω), R2 (Ω) and the Voltage divider calculator works out Output voltage (V) straight away. For instance, with Input voltage (V) = 12, R1 (Ω) = 1,000 and R2 (Ω) = 2,000 it returns Output voltage (V) = 8.

How to use it

  1. Enter your values: Input voltage (V), R1 (Ω), R2 (Ω).
  2. Read the result instantly: Output voltage (V).

Frequently asked questions

What does the Voltage divider calculator actually compute?

It takes Input voltage (V), R1 (Ω) and R2 (Ω) and derives Output voltage (V) from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

3 values: Input voltage (V), R1 (Ω) and R2 (Ω). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Input voltage (V) = 12, R1 (Ω) = 1,000 and R2 (Ω) = 2,000, the calculator returns Output voltage (V) = 8. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Input voltage (V) = 24, R1 (Ω) = 2,000 and R2 (Ω) = 4,000 instead, Output voltage (V) goes from 8 to 16 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Input voltage (V) = 6, R1 (Ω) = 500 and R2 (Ω) = 1,000, Output voltage (V) comes out at 4. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Putting a number on a bill: what an appliance costs to run, whether a solar array covers the load, and how much heating a room actually needs.

What is the most common mistake?

Confusing power with energy. A kilowatt is a rate and a kilowatt-hour is a quantity; a 2 kW heater on for half an hour uses 1 kWh, and only the second figure appears on a bill.

What is the difference between the Voltage divider calculator and the Voltage drop calculator?

This one returns Output voltage (V); the Voltage drop calculator returns Voltage drop (V) and Voltage drop (%). That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Amperage Calculator is the closest one after this: Convert a load in watts and a supply voltage into the current drawn in amps.

Where do the figures come from, and how current are they?

The arithmetic is exact for the rating and the tariff you enter. Nameplate wattage is a maximum, not an average, and solar output depends on latitude, orientation and shading that no formula can guess.

Further reading

All guides →
ExplainerThe Voltage Divider: The Formula Is Trivial, the Assumption Behind It Is NotVout = Vin·R2/(R1+R2) is only true when nothing is connected to the output. Draw current and the voltage collapses, by an amount that follows one exact law. Here is that law, the ten-times rule checked against it, and why a lower-resistance divider costs you power forever.How-toHow Much Does a Space Heater Cost to Run?Multiply the heater's kilowatts by hours used and your price per kWh — a 1.5 kW heater for 5 hours a day adds up fast at typical tariffs.How-toHow Many Amps Does an Appliance Draw?Divide the appliance wattage by the supply voltage to get the current in amps — the number that decides breaker size, wire, and what can share a circuit.How-toWhat Wire Gauge Do I Need?Pick wire size from the load current, run length, and allowed voltage drop — the amps decide the minimum cross-section, distance forces you thicker.ExplainerWhat Is Voltage Drop? Why Long Wires Lose VoltageVoltage drop is the voltage lost along a wire due to its resistance. Learn how length, gauge, and current affect it, and why it matters for your circuits.ExplainerHow Many Cables Fit in a Conduit? It Is a Code Question, Not a Geometry QuestionThe 40 % limit for three or more conductors is not about whether they physically fit. It is about heat and about pulling them in without stripping the insulation — and the moment you use that space, the code takes current away from every conductor in the pipe.