Belvanta Electricals has quarterly revenue of Rs 1,000 crore, a 35% contribution margin and Rs 200 crore of fixed costs. Consensus assumes 12% volume growth and 3% price growth; your channel checks say volume grows 8%. How big is the EBIT miss?

Consensus implies EBIT of about Rs 225.6 crore; your checks imply Rs 210.4 crore, a miss of about 6.7%. Revenue is only 3.6% lower, Rs 1,153.6 crore against Rs 1,112.4 crore, but fixed costs of Rs 200 crore do not move, so every rupee of lost contribution falls straight to EBIT. The miss is about 1.9 times the revenue gap.

Split revenue into its drivers and let each hit costs the way it really does. Volume moves both revenue and variable costs; price moves revenue only, because each fan costs the same to make whatever it sells for. So consensus revenue is 1,000 x 1.12 x 1.03 = Rs 1,153.6 crore, and variable costs are 650 x 1.12 = Rs 728 crore. Contribution is Rs 425.6 crore; take off Rs 200 crore of fixed costs and consensus EBIT is Rs 225.6 crore. Your version swaps 1.12 for 1.08: revenue Rs 1,112.4 crore, variable costs Rs 702 crore, EBIT Rs 210.4 crore.

Think of a tea stall that pays Rs 20,000 a month in rent whatever it sells. Sell 10% fewer cups and revenue falls 10%, but the rent does not, so profit falls much more than 10%. Belvanta's fixed costs play the rent: the lost volume removes Rs 15.2 crore of contribution and none of the Rs 200 crore of fixed cost, so EBIT falls 6.7% on a 3.6% revenue gap. The ratio, about 1.9, is the operating leverageHow much operating profit moves for a given move in revenue, driven by the share of costs that are fixed. It works in both directions. at this point, and it is why small volume disagreements turn into large earnings surprises.

The shortcut is to hold the margin at 35% and apply it to the revenue gap: Rs 41.2 crore x 35% = Rs 14.4 crore. That understates the miss, because a 3% price rise on flat unit costs lifts the margin on every unit, including the ones you think will not sell. Here the error is under a crore, and the flat-margin version still gives a miss of about 7.1%. Say which method you used; on a company with larger price moves the gap between the two methods grows.

Finish with what you would do with it. A 7% EBIT miss is large enough to move a stock if the market has not already priced it, so the next questions are how confident the channel checks are, whether the missing volume is timing, such as a late summer, or share loss, and what the company said about volume at its last call. The number starts the conversation; it does not end it.