Voltage Divider Input Form
Enter source voltage, choose the tap position, add resistor values, and optionally include a load resistor connected from the tap node to ground.
Formula Used
1) Unloaded divider output
Vout = Vin × (Rlower / (Rupper + Rlower))
2) Loaded divider output
First combine the lower branch and load:
Req = (Rlower × RL) / (Rlower + RL)
then calculate
Vout = Vin × (Req / (Rupper + Req)).
3) Source and branch currents
Isource = Vin / (Rupper + Req),
Ilower = Vout / Rlower,
and
Iload = Vout / RL.
4) Voltage drop and power
Resistor drop is
V = I × R,
and dissipation is
P = I² × R.
5) Thevenin equivalent at the tap
Vth = unloaded Vout
and
Rth = (Rupper × Rlower) / (Rupper + Rlower).
How to Use This Calculator
Step 1
Enter the source voltage applied across the full resistor chain.
Step 2
Choose how many series resistors are active in the divider network.
Step 3
Select the output tap location. The tap is measured between two adjacent active resistors.
Step 4
Enter each resistor value in ohms. Only the active resistor fields are used.
Step 5
Leave the load resistance blank for an unloaded divider, or enter RL to model loading.
Step 6
Click the calculate button. The result appears above the form, followed by the graph and detailed tables.
Step 7
Use the export buttons to download a CSV file or a PDF summary for reports and design reviews.
Example Data Table
| Example | Vin (V) | Resistors (Ω) | Tap After | RL (Ω) | Unloaded Vout (V) | Loaded Vout (V) |
|---|---|---|---|---|---|---|
| Basic two resistor divider | 12 | 1000, 2000 | R1 | Blank | 8.0000 | 8.0000 |
| Three resistor tap with load | 24 | 1000, 2200, 3300 | R1 | 10000 | 20.3077 | 18.7273 |
| Four resistor lower tap | 9 | 470, 680, 1000, 2200 | R2 | 4700 | 6.6292 | 5.6007 |
Frequently Asked Questions
1. What does this voltage division calculator solve?
It calculates unloaded and loaded output voltage, total current, branch current, resistor drops, power dissipation, divider ratio, and Thevenin values for a tapped series resistor network.
2. What is the output tap location?
The tap location is the node between two active resistors. The calculator treats everything above the tap as the upper branch and everything below it as the lower branch.
3. Why does the loaded output differ from the unloaded output?
A load resistor draws extra current from the tap node. That changes the effective lower resistance and pulls the output voltage lower than the unloaded divider value.
4. Can I use more than two resistors?
Yes. This file supports up to six series resistors and lets you choose different tap positions. That helps model stepped reference networks and multi-section dividers.
5. What units should I enter?
Enter voltage in volts and resistance in ohms. Current is returned in amperes and power is returned in watts.
6. What is Thevenin resistance here?
It is the equivalent resistance seen looking back into the tap node when the source is shorted. It helps estimate how strongly a future load will affect the divider.
7. Does this calculator show resistor heating information?
Yes. Each active resistor includes calculated power dissipation. You can compare those results against resistor wattage ratings when selecting safe component values.
8. When should I leave RL blank?
Leave RL blank when you want the ideal unloaded divider voltage. Add RL when the output feeds another circuit stage, sensor input, or measurement path.