Calculation of equivalent resistance

If a circuit is the combination of many resistors one can simplify the calculations by merging them in step by step until there is only one single equivalent resistance left, R_ERS.
See example below.

• Resistors R₂ and R₃ are in parallel and can be merged into one resistor R₂₃.
  
• Resistors R₄ och R₅ are in parallel and can be merged into one resistor R₄₅.
  

• Resistors R₂₃ och R₄₅ are in series and can be added to one resistor R₂₃₄₅ = R₂₃ + R₄₅.

• Resistors R₁ och R₂₃₄₅ are in parallel and can be merged into one resistor R₂₃₄₅₁.
  

Thus, all five resistors are replaced by one single R_ERS = R₂₃₄₅₁.