The Transformer Turns Ratio Calculator calculates the turns ratio of a transformer, which relates the primary and secondary coil turns to the respective voltages. The turns ratio is determined using N₁/N₂ = V₁/V₂, where N₁ and N₂ are the number of turns on the primary and secondary coils, and V₁ and V₂ are the primary and secondary voltages. This is essential for designing transformers and understanding voltage step-up or step-down in AC circuits.