Voltage Divider Calculator
Calculate the output of a two-resistor divider and the current it draws.
A divider is not a power supply
The formula assumes nothing draws current from the output. Connect a load comparable to R₂ and the output sags, because the load sits in parallel with R₂. Dividers suit reference voltages and sensing; anything drawing real current needs a regulator.
What this page needs from you
This page asks for input voltage in V, r1 (top) in Ω and r2 (bottom) in Ω. From those it returns output voltage in V, together with divider current, power dissipated, division ratio and r2 needed for 5 v out. Every figure updates as you type, and nothing you enter leaves your browser.
Check the power rating, not just the value
Choosing a component by its resistance or capacitance alone leaves out the rating that actually determines whether it survives. Work out the power the part will dissipate and pick something rated for at least twice it: a resistor run at its limit gets hot enough to drift out of tolerance and to discolour the board.
The formula
V_out = V_in · R₂ / (R₁ + R₂)
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Voltage Divider Calculator
- Fill in each field with your own figures — the defaults are only there as an example.
- The result updates as you type, so there is no button to press.
- Check the breakdown under the main result for the supporting numbers.
- Use the copy button to take the result with you, or share the link to reload the same inputs.
Voltage Divider Calculator — frequently asked questions
Is this voltage divider calculator free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
How accurate is the result?
The maths is exact for the formula shown on the page. Accuracy in the real world depends on your inputs and on assumptions the formula cannot see, so treat the output as a well-grounded estimate rather than a quote.
Can I use it on my phone?
Yes. The page is responsive, weighs a few kilobytes and works offline once loaded, so it behaves the same on a phone as on a desktop.
What people search for
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed September 14, 2026 · Calculation runs client-side · No data collected · Report an error