# Voltage Divider Calculator

Voltage divider calculator calculates the voltage drops on each resistor load, when connected in series. Enter total voltage supply and press the Calculate button:

### Enter input:

Total voltage: VT = Volts [V]
Resistance of first load: R1 = Ohms [Ω]
Resistance of second load: R2 = Ohms [Ω]

(optional)

R3 = Ohms [Ω]

### Voltage Drop Results:

Voltage drop in R1: V1 = Volts [V]
Voltage drop in R2: V2 = Volts [V]
Voltage drop in R3: V3 = Volts [V]

## Voltage divider rules

### Voltage divider rule for DC circuit

For a DC circuit with constant voltage source VT and resistors in series, the voltage drop Vi in resistor Ri is given by the formula:

Where:

Vi – voltage drop in resistor Ri in volts [V]
VT
– the equivalent voltage source or voltage drop in volts [V]
R
i – resistance of resistor Ri in ohms [Ω]
R
1 – resistance of resistor R1 in ohms [Ω]
R
2 – resistance of resistor R2 in ohms [Ω]
R
3 – resistance of resistor R3 in ohms [Ω]

#### Example

Voltage source of VT=30V is connected to resistors in series, R1=30Ω, R2=40Ω. Find the voltage drop on resistor R2.

V2 = VT × R2 / (R1+R2) = 30V × 40Ω / (30Ω+40Ω) = 17.14V

### Voltage divider for AC circuit

For an AC circuit with voltage source VT and loads in series, the voltage drop Vi in load Zi is given by the formula:

Vi – voltage drop in load Zi in volts [V].
VT – the equivalent voltage source or voltage drop in volts [V].
Zi – impedance of load Zi in ohms [O].
Z1 – impedance of load Z1 in ohms [O].
Z2 – impedance of load Z2 in ohms [O].
Z3 – impedance of load Z3 in ohms [O].

#### Example

Voltage source of VT=30V∟60° is connected to loads in series, Z1=30Ω∟20°, Z2=40Ω∟-50°.

Find the voltage drop in load Z1

V2 = VT × Z1 / (Z1+Z2)

= 30V∟60° × 30Ω∟20° / (30Ω∟20°+40Ω∟-50°)

= 30V∟60° × 30Ω∟20° / (30cos(20)+j30sin(20)+40cos(-50)+j40sin(-50))

= 30V∟60° × 30Ω∟20° / (28.19+j10.26+25.71-j30.64)

= 30V∟60° × 30Ω∟20° / (53.9-j20.38)

= 30V∟60° × 30Ω∟20° / 57.62Ω∟-20.71°

= (30V×30Ω/57.62Ω) ∟ (60°+20°+20.71°)

= 15.62V∟100.71°

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1. Dan
Aug 01, 2014

Why do you need a software? Pretty easy to calculate on paper.

Also, very easy to program in a software too.

2. dileep kumar gupta
May 23, 2014