1Equal resistors (10kΩ each, 12V)
Inputs
Vin12 V
R110,000 Ω
R210,000 Ω
Result
Vout6.000 V
Current0.60 mA
Vout = 12 × 10000/(10000+10000) = 12 × 0.5 = 6.000V. I = 12/20000 = 0.6mA.
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Voltage Divider Calculator
Output Voltage
6.000 V
Ratio
50.0%
Current
0.60 mA
Output Voltage (Vout)
6.000 V
Divider Ratio
50.0%
Current
0.60 mA
R1 Power
3.6 mW
R2 Power
3.6 mW
What You'll Need
ELEGOO 120pcs Multicolored Dupont Wire 40pin Male to Female, 40pin Male to Male, 40pin Female to Female Breadboard Jumper Wires Ribbon Cables Kit Compatible with Arduino Projects
$6.98
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WWZMDiB 840 Pin Breadboard Jumper Wires Kit 14 Vaules 2-125mm
$8.99
View on Amazon
EDGELEC 120pcs Breadboard Jumper Wires 20cm Wire Length Optional Dupont Cable Assorted Kit Male to Female Multicolored Ribbon Cables
$6.98
View on AmazonELEGOO 120pcs Multicolored Dupont Wire 40pin Male to Female, 40pin Male to Male, 40pin Female to Female Breadboard Jumper Wires Ribbon Cables Kit Compatible with Arduino Projects
$6.98
View on AmazonWWZMDiB 840 Pin Breadboard Jumper Wires Kit 14 Vaules 2-125mm
$8.99
View on AmazonEDGELEC 120pcs Breadboard Jumper Wires 20cm Wire Length Optional Dupont Cable Assorted Kit Male to Female Multicolored Ribbon Cables
$6.98
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Price as of Jul 24, 2026. Product prices and availability are accurate as of the date indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
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Disclaimer: This calculator provides preliminary estimates for educational purposes only. It is not a substitute for a licensed professional engineer, architect, or structural engineer. Results depend on material grade and species, site conditions, local climate and snow loads, and amendments to the applicable building code, all of which vary by location. Always verify results against your local building codes and confirm requirements with your Authority Having Jurisdiction before proceeding. Do not use these estimates for permitting, fabrication, or construction without stamped, engineer-sealed drawings from a licensed professional. Improperly sized structural members, foundations, or gas lines can cause structural collapse, fire, gas leaks, serious injury, or death.
Example Calculations
25V to 3.3V (10kΩ + 20kΩ)
Inputs
Vin5 V
R110,000 Ω
R220,000 Ω
Result
Vout3.333 V
Current0.17 mA
Vout = 5 × 20000/(10000+20000) = 5 × 0.667 = 3.333V. I = 5/30000 = 0.167mA.
Frequently Asked Questions
QWhat is a voltage divider?
A voltage divider uses two series resistors to produce an output voltage that is a fraction of the input. Vout = Vin × R2 / (R1 + R2). Equal resistors give half the input voltage.
- Two resistors in series between Vin and ground
- Output taken from the junction between R1 and R2
- Vout = Vin × R2/(R1+R2)
- Equal resistors: Vout = Vin/2
| R1 | R2 | Ratio | Vout (12V in) |
|---|---|---|---|
| 10kΩ | 10kΩ | 50% | 6.000V |
| 10kΩ | 20kΩ | 66.7% | 8.000V |
| 20kΩ | 10kΩ | 33.3% | 4.000V |
| 10kΩ | 4.7kΩ | 32.0% | 3.837V |
QHow does a load affect a voltage divider?
A load in parallel with R2 reduces the effective R2, lowering Vout. The heavier the load (lower resistance), the more Vout drops. Rule of thumb: load should be at least 10x R2 for minimal effect.
- Load parallels R2: R2_eff = R2×Rload/(R2+Rload)
- Lower load resistance = more Vout drop
- Rule: Rload > 10×R2 for <10% error
- No-load Vout is theoretical maximum
QHow do I choose R1 and R2 values?
Start with desired ratio: R2/(R1+R2) = Vout/Vin. Higher total resistance wastes less power but is more sensitive to load. 10kΩ total is common for signal circuits; 1kΩ for power.
- Calculate ratio: Vout/Vin
- Pick R2, then R1 = R2×(Vin/Vout - 1)
- Higher R: less current waste, more load-sensitive
- Lower R: more waste, better load regulation
QCan I use a voltage divider as a power supply?
Not recommended. Voltage dividers cannot regulate voltage under changing load—output drops as current increases. Use a voltage regulator (LM7805, LDO) for stable DC supply.
- No regulation: Vout changes with load
- Inefficient: wasted power in R1
- Use for: reference voltages, ADC scaling, biasing
- Do not use for: powering ICs, motors, LEDs
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Last Updated: Jul 24, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.