Formula (equation) for the calculation of two resistances R1 and R2 connected in parallel:
Calculation of the necessary parallel resistor R2, when R1 and the total resistance Rtotal is given:
Solving the formula Rt= (R1× R2) / (R1 + R2) for R1:
The first step is to clear all fractions by multiplying by the lowest
common denominator, that is Rt × R1 × R2 ... so we get:
1/Rt = 1/R1 + 1/R2
Rt × R1 × R2[1/Rt = 1/R1 + 1/R2]
R1 × R2 = Rt × R2 + Rt × R1 then collect terms with R1 and solve
R1 × R2 − Rt × R1 = Rt × R2
R1(R2 − Rt) = R2 × Rt
R1 = R2 × Rt / (R2 − Rt)
R2 = R1 · Rges / (R1 − Rges)
Notice: This calculator can also solve other math problems. Calculating resistors in parallel is
precisely the same as the calculations required for inductors in parallel or for capacitors in series.
|Two resistors in parallel and the resulting total resistance: Two of the same value, also show the equation that the results are always half. That makes it easier when designing circuits or prototyping. With caps it's always double, then again caps just simply add up in parallel.|
• Search resistances R1 and R2, when the target resistance (equivalent resistance) is known •
Calculation: Resistor pairs - reverse engineered calculator
Search of R1 and R2 with known target resistance
● Calculate many resistors in parallel ●
|This calculator determines the resistance of up to 10 resistors in parallel.
Enter resistances into the boxes below and when all values have been input,
click on the 'calculate' button and the result will appear in the box below that button.
As a test, if we enter resistances of 4, 6, and 12 ohms, the answer should be 2 ohms.
Notice: Manually clearing the boxes does not reset stored values. Use "reset".
Ohm's law - calculator and formulas
Two resistors in parallel and the resulting total resistance
Resistance ranging from 1 ohm to 100 ohms
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