Enter exactly four positive resistances in ohms (Ω) and the shared DC supply voltage in volts (V). Results show equivalent resistance in Ω and currents in amperes (A).
Each resistance accepts 0.001–1,000,000 Ω; voltage accepts 0–1,000 V. Convert kilohms to ohms before entering values: 1 kΩ = 1,000 Ω. All four branches must be present; zero is not a way to disable a branch.
Values use fixed units stated in the labels. The calculator stores these as scalar numbers using the registered unit 1; it does not perform electrical unit conversion.
The calculator combines two resistors using Rparallel = Ra × Rb / (Ra + Rb), first for R1 and R2, then for R3 and R4, then for the two equivalent pairs. This equals the four-term reciprocal formula and remains valid at zero supply voltage. Each branch current follows Ohm’s law. See NASA: Resistors in Parallel.
Assumptions: ideal fixed resistors, negligible wire resistance and an ideal DC voltage source. Resistor tolerance, heating, source current limits and component power ratings are not modeled. Input bounds define the calculator’s numerical scope, not component ratings.
Invalid or unavailable results must not be interpreted as zero. Displayed values are rounded to eight decimal places; very small positive currents may round to zero.
| Supply voltage (V) | R1, R2, R3, R4 (Ω) | Equivalent resistance (Ω) | I1, I2, I3, I4 (A) | Total current (A) |
|---|---|---|---|---|
| 12 | 100, 200, 300, 600 | 50 | 0.12, 0.06, 0.04, 0.02 | 0.24 |
| 5 | 1000, 1000, 1000, 1000 | 250 | 0.005, 0.005, 0.005, 0.005 | 0.02 |
| 0 | 100, 200, 300, 600 | 50 | 0, 0, 0, 0 | 0 |
For 100, 200, 300 and 600 Ω, the reciprocal sum is 0.01 + 0.005 + 0.003333… + 0.001666… = 0.02 Ω⁻¹. Its reciprocal is 50 Ω. At 12 V, the branch currents are 12/100 = 0.12 A, 12/200 = 0.06 A, 12/300 = 0.04 A and 12/600 = 0.02 A. Their sum is 0.24 A, matching 12/50.
For four equal 1,000 Ω resistors, equivalent resistance is 1,000/4 = 250 Ω. At 5 V each branch carries 0.005 A and the supply delivers 0.02 A.
Formula source
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