Calculate how much your sales need to increase to maintain profit when offering discounts. Understand the real impact of promotions on your bottom line.
What this means: To maintain the same total profit when offering a 20% discount with 40% COGS, you need to sell 50.0% more units. Your margin per unit drops from 60.0% to 40.0%, so higher volume is required to compensate.
Your original profit margin = 100% - COGS%. For example, if your COGS is 40%, your margin is 60%.
When you offer a discount, your new selling price = 100% - Discount%. Your new margin = New Price - COGS. A 20% discount on an item with 40% COGS means you sell at 80% price, leaving 40% margin.
To maintain the same total profit with lower per-unit margin, calculate: (Original Margin / New Margin - 1) x 100. With 60% original margin and 40% new margin, you need (60/40-1) x 100 = 50% more sales.
Use this data to decide if the discount makes sense. Can you realistically achieve the required volume increase? Will the discount drive enough new customers or larger orders to hit the target?
Discounts can feel like "free" marketing, but they directly cut into your bottom line. A 20% discount doesn't mean 20% less profit - it often means 40-50% less profit per sale.
Before running a promotion, know exactly how much more you need to sell. If you need a 67% sales increase to break even on a 25% discount, is that realistic?
Not all discounts are created equal. A 10% discount with 30% COGS requires 14% more volume. A 30% discount requires 75% more volume. Find the sweet spot.
When you discount to acquire new customers, factor in the margin erosion. Your effective CAC is higher than you think when discounts are involved.
Before launching Black Friday, flash sales, or clearance events, calculate how much volume you need to hit to maintain profitability.
When planning promotional email campaigns, test different discount levels. A 15% discount might require 21% more sales while 25% requires 50% more.
When offering volume discounts or wholesale pricing, ensure the lower margin is offset by higher order quantities.
Before giving influencers 20% discount codes, calculate if their audience size and conversion rate can drive enough volume.
When creating winback campaigns for lapsed customers, balance discount depth with expected response rate.
Sales volume increase required to maintain the same total profit, by discount depth and COGS. Notice how fast the numbers grow: at 60% COGS, a 20% discount already requires doubling your sales.
The maximum discount before you sell at a loss is your original margin: max discount% = 100% - COGS%. With 40% COGS the ceiling is 60% off. Beyond it, every additional sale loses money, so more volume makes the promotion worse, not better.
Long before the hard ceiling, the required volume lift becomes unrealistic. A useful gut check: a discount that cuts your remaining margin in half requires doubling your sales just to break even on total profit. Set your discount by working backwards from the lift you can realistically expect a promotion to drive, not from what competitors are offering.
This calculator uses COGS for simplicity, but shipping, transaction fees, and fulfillment also come out of every order. Your true per-order margin is thinner than 100% - COGS%, which means the real volume lift you need is higher than the headline number. Use our contribution margin calculator (linked below) for the full per-order picture.
The same math works for permanent markdowns, not just limited-time promotions. Your sale price is the original price times (1 - discount%): a $50 product marked down 20% sells at $40. Enter the markdown as the discount percentage above to see what it does to your margin and how much extra volume the lower price has to generate.
The one difference is the goal. A promotion should replace the profit it gives away, so the required volume lift is the test that matters. Clearance is about recovering cash from inventory that will not sell at full price, so a markdown that fails the volume test can still be the right decision when the alternative is dead stock.
Discount margin is the profit margin left on a sale after applying a discount. The formula: new margin = (100% - discount%) - COGS%. If your COGS is 40% and you offer a 20% discount, you sell at 80% of the original price and keep a 40% margin, down from 60% at full price.
Required volume increase = (original margin / new margin - 1) x 100. If a discount drops your margin from 60% to 40%, you need (60/40 - 1) x 100 = 50% more units to earn the same total profit. Deeper discounts require disproportionately more volume.
Because the discount comes entirely out of your margin, not the full price. With 40% COGS, a 20% discount cuts per-unit profit by a third (from a 60% margin to 40%). The higher your COGS, the harder each point of discount hits your profit.
When the discount equals or exceeds your original margin, meaning discount% >= 100% - COGS%. At that point every sale loses money, and no amount of extra volume can make the promotion profitable.
Your break-even ceiling is your original margin: max discount% = 100% - COGS%. With 40% COGS you can discount up to 60% before selling at a loss. In practice you want to stay well below the ceiling, because as the discount approaches it, the required volume increase grows toward infinity. A discount that leaves half your original margin intact requires doubling your volume to break even on profit.
Sale price = original price x (1 - discount%). A $50 product at 20% off sells for $40. To see what that does to profit, compare the sale price against your unit cost: if the product costs $20, your per-unit profit drops from $30 to $20, a 33% cut from a 20% discount.
Compare the dollar cost per order. Free shipping is a roughly fixed cost, while a percentage discount scales with order value. On an $80 order, a 10% discount costs $8; if your average shipping cost is $6, free shipping is the cheaper incentive. The higher your average order value, the more a percentage discount costs relative to free shipping.
Yes, the margin math is identical: a markdown is a discount that does not end. The difference is the goal. A promotion needs the volume lift to replace lost profit, while clearance is usually about recovering cash from inventory that will not sell at full price, so selling below original margin (sometimes below cost) can still be the right call.
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