Assign any current direction you like. If the answer comes out negative, the current flows the other way — the magnitude is still right.
People stall on multi-loop circuits trying to reason out directions first. You do not have to. Kirchhoff’s laws are linear, so a wrong guess produces a correct negative number rather than a wrong answer. The only rule that matters is consistency: once you have drawn the arrows, write every equation to match them and do not change your mind halfway.
The sign convention only forgives you if you keep it. Assign directions, then write every equation to match those arrows, including the polarity of every voltage drop — flip your mind halfway through one loop and the algebra produces a confident, consistent, wrong answer.
Estimate with the rule, then check it against the calculator that models it properly.
Open Electrical Circuit →Assign any current direction you like. If the answer comes out negative, the current flows the other way — the magnitude is still right. People stall on multi-loop circuits trying to reason out directions first.