Discount impact calculator
Find the extra units needed to preserve contribution after a price discount.
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Your results
Required volume preserves contribution mathematically; it does not forecast demand or assume buyers will respond to the discount.
- Discounted price
- £48.00
- Original price after the stated discount.
- Contribution/unit
- £13.00
- At unchanged variable cost.
- Required whole units
- 193
- Rounded up to preserve original total contribution.
- Additional whole units
- 93
- Extra units needed, not a demand forecast.
- Unrounded sales uplift
- 92.31%
- The mathematical uplift before rounding whole units.
How to use this tool
Use one reporting window and a consistent measurement scope. Replace the example inputs with your own figures. The result updates locally as you type. Copy the result to your planning notes, or copy a link containing only the numeric inputs. Reset restores the illustrative example.
- Enter price, cost per order and the discount.
- Read the margin after the discount.
- Read how many extra sales are needed to earn the same profit.
- Decide whether that volume is realistic for your traffic.
Worked example
A £60 item costing £35 contributes £25. At 20% off, the £48 selling price contributes £13. Preserving £2,500 total contribution requires 193 units instead of 100. That is 93 additional whole units. The underlying unrounded uplift is 92.3%.
Formula and units
Original contribution/unit = price - variable cost. Discounted contribution/unit = price × (1 - discount%) - variable cost. Required units = ceil(original units × original contribution / discounted contribution).
Assumptions and review notes
This comparison holds variable cost per unit and fixed marketing spend constant. It does not assume the discount will create the required demand. If the reduced price is at or below variable cost, extra sales cannot preserve a positive contribution. Price-dependent fees, shipping thresholds and bundles may require a fuller order-level model.
Discounts cut margin sharply, so the volume needed rises faster than the discount. A discount can still make sense for clearance or acquiring repeat customers, if you know that is the aim.
- Starting margin.
- Size of discount.
- Demand elasticity.
- Effect on repeat buying.
- Judging a discount by revenue.
- Ignoring ad cost at the new margin.
- Assuming volume will rise.
- Training customers to wait for sales.
A closer look
Common questions.
- How are extra sales calculated?
- Original profit divided by profit after discount, minus one.
- Is a bigger discount better?
- Not necessarily. It raises the volume needed.
- Should I include ad cost?
- Yes, since break-even ROAS rises as margin falls.
- Do discounts bring repeat buyers?
- Sometimes, but verify in your data.
- Does it store data?
- No.