Offer comparison: How to calculate if a 20% discount beats a $15 flat markdown
The Trap: Assuming 20% Always Beats a Flat $15 Off
Most buyers see "20% off" and their brain lights up. Twenty percent sounds substantial. It sounds like a fifth of the price vanishing. Meanwhile, "$15 off" feels modest — like a coupon you'd clip from a Sunday flyer. So the instinct is obvious: grab the percentage deal, skip the flat markdown, move on.
This is wrong roughly half the time.
If you're a small reseller, dropshipper, or side-hustle seller who sources inventory from multiple suppliers — each running different promotional structures — this instinct is quietly eating your margins. You don't need a finance degree to fix it. You need a simple, repeatable workflow that takes about thirty seconds per purchasing decision and guarantees you always pick the offer that puts more money back in your pocket.
Let's walk through that workflow from start to finish.
Why Your Gut Instinct Fails You Here
The Percentage Illusion
Percentages are slippery because their value changes with the price tag. A 20% discount on a $50 item saves you $10. On a $200 item, that same 20% saves you $40. The number "20" stays constant, but what it actually delivers swings wildly depending on what you're buying.
Flat markdowns don't have this problem. Fifteen dollars is fifteen dollars, whether you're spending $30 or $300. That stability is underrated.
The Real Question You Should Be Asking
Instead of asking "which discount sounds better," the question every reseller should ask is simple: at what cart total does 20% equal $15?
That number — the point where both offers produce identical savings — is called the breakpoint. Once you know it, every comparison becomes a five-second judgment call.
The Breakpoint: Where 20% and $15 Meet
Here's the math, stripped down to its bones.
You want to find the order total where both discounts save you the exact same amount. So you set them equal:
0.20 × Order Total = $15
Solve for the order total:
Order Total = $15 ÷ 0.20 = $75
That's your breakpoint. $75.
Below $75, the flat $15 markdown saves you more. Above $75, the 20% discount pulls ahead. At exactly $75, it's a tie.
Think of it like a seesaw. The $75 mark is the fulcrum — the balance point. Tip your cart total to one side, and one discount becomes heavier. Tip it to the other, and the opposite discount wins.
Quick Reference: How the Savings Shift
Let's make this concrete with real numbers so you can see the crossover in action:
- $40 order: 20% saves $8 | $15 flat saves $15 → Flat wins by $7 - $60 order: 20% saves $12 | $15 flat saves $15 → Flat wins by $3 - $75 order: 20% saves $15 | $15 flat saves $15 → Tie - $90 order: 20% saves $18 | $15 flat saves $15 → 20% wins by $3 - $120 order: 20% saves $24 | $15 flat saves $15 → 20% wins by $9
Notice how the gap widens as you move away from $75 in either direction. The further your order total sits from the breakpoint, the more money you're leaving on the table by choosing the wrong offer.
Step-by-Step: Your Offer Comparison Workflow
Now let's turn this into a practical workflow you can run every time you're staring at two supplier promotions. Five steps, end to end.
Step 1: Calculate Your Pre-Discount Cart Total
Add up everything you plan to order before any discounts apply. This sounds obvious, but resellers routinely forget to include shipping, handling fees, or small add-on items they toss into the cart at the last second. Your total must reflect what you're actually paying for goods — nothing more, nothing less.
Let's say you're restocking inventory from a wholesale supplier. Your cart contains:
- 10 units of Product A at $8 each = $80 - 5 units of Product B at $6 each = $30 - 2 units of Product C at $12 each = $24
Pre-discount total: $134
Step 2: Identify Your Breakpoint
You already know this one. For a 20% versus $15 comparison, the breakpoint is $75.
But here's where a discount calculator becomes invaluable: if the offers change — say, next month your supplier runs 15% off versus $20 flat — you need to recalculate. The formula stays the same:
Breakpoint = Flat Markdown ÷ Percentage (as a decimal)
For 15% vs. $20: $20 ÷ 0.15 = $133.33
For 25% vs. $10: $10 ÷ 0.25 = $40
Memorize the formula. Or better yet, bookmark a discount calculator tool so you never have to do it manually.
Step 3: Compare Your Total to the Breakpoint
This is the moment of decision. Your pre-discount total is $134. Your breakpoint is $75.
Since $134 is well above $75, the 20% discount wins. The math confirms it: 20% of $134 is $26.80 in savings, compared to just $15 from the flat markdown. That's an $11.80 difference — real money that stays in your business bank account.
Had your total been $60 instead, you'd flip the decision. At $60, the flat $15 markdown saves you $3 more than the 20% discount would.
Step 4: Check for Thresholds and Caps
This is the step most resellers skip — and it's where suppliers quietly claw back value.
Some percentage discounts cap out. "20% off, maximum savings of $20" means once your order exceeds $100, the percentage stops working in your favor. At your $134 total, you'd only save $20, not $26.80. Suddenly the flat $15 markdown isn't looking so far behind — and if there were a minimum purchase requirement on the flat offer, the dynamics shift again.
Other promotions require minimum order quantities, exclude certain product categories, or only apply to first-time buyers. Read the fine print before you commit.
Step 5: Lock In the Better Offer
Once you've confirmed the math and checked the terms, apply the winning discount code to your cart. Then verify the final price actually reflects the savings you calculated. Suppliers' checkout systems occasionally fail to apply promotions correctly — especially when you stack items from different categories.
If the numbers don't match your calculation, don't checkout. Re-run the workflow. Thirty seconds of verification beats a silent margin leak you won't notice until month-end.
When the Flat Markdown Wins (And When It Doesn't)
Understanding when each discount type wins makes you faster at spotting good deals without running the full calculation every time.
Flat Markdowns Favor Small Orders
If you're placing a test order — sampling a new product, restocking a single fast-moving SKU, or buying a one-off item — your cart total probably sits below $75. In this territory, the flat $15 markdown almost always wins.
This is why flat markdowns are particularly valuable for new resellers validating suppliers. Your early orders tend to be small and cautious. A $15 savings on a $40 order represents a 37.5% effective discount — far better than the advertised 20%.
Percentage Discounts Favor Bulk Restocks
When you're confident in a product's sell-through rate and ready to place a larger restock order, your cart total climbs past $75. Now the percentage discount flexes its muscle. The larger your order, the more dramatic the gap becomes.
At a $300 restock order, 20% saves you $60 compared to $15 flat. That's $45 in additional savings — enough to cover shipping on your next two orders.
The Danger Zone: Orders Near the Breakpoint
Orders between $65 and $85 are where most resellers make mistakes. The savings difference is small enough to feel negligible — $2 or $3 — so people pick whichever offer "feels right" and move on. But if you place twenty orders per month in that range, picking wrong each time costs you $40 to $60 monthly. Over a year, that's $480 to $720 in avoidable losses.
Small leaks sink ships. Run the calculation every time.
Common Pitfalls Even Experienced Resellers Make
Pitfall 1: Comparing Post-Discount Prices Instead of Savings
Some resellers calculate the final price under each discount and pick the lower one. This works, but it's slower and introduces more opportunities for arithmetic errors. Comparing savings directly — "which discount puts more money back?" — is faster and more intuitive.
Pitfall 2: Forgetting That Sales Tax Complicates Things
If your supplier charges sales tax, the tax is usually calculated on the pre-discount total in some jurisdictions and the post-discount total in others. This can subtly shift the breakpoint. For most resellers with resale certificates, this isn't an issue — but if you're buying for personal use or don't have a certificate yet, factor tax into your final comparison.
Pitfall 3: Ignoring Shipping Thresholds
Many suppliers offer free shipping once your order crosses a certain threshold — say, $100. If your pre-discount total is $95 and you're choosing between 20% off and $15 off, the decision isn't just about the discount itself. The 20% discount reduces your total to $76, which might drop you below the free shipping threshold. The $15 markdown reduces your total to $80 — still below $100.
In this scenario, you might need to add a $5 item to your cart to hit free shipping, which changes your entire calculation. Always consider the total cost of ownership, not just the headline discount.
Turning This Into a Repeatable Habit
The resellers who consistently pick the right discount aren't doing complex math every time. They've internalized one number — the breakpoint — and built a reflex around it.
Here's how to make it automatic:
First, memorize the current breakpoint for the offers you see most often. If your primary supplier runs 20% versus $15 frequently, $75 is your magic number. Tattoo it on your brain.
Second, use a discount calculator for anything unusual. New percentage? Different flat amount? Minimum purchase requirement? Thirty seconds with a calculator beats thirty minutes of regret.
Third, batch your orders strategically. If your cart sits at $68 — just below the breakpoint — consider whether adding a $10 item you'll need anyway pushes you past $75 and unlocks better percentage savings. Sometimes the smartest move isn't choosing between two discounts; it's restructuring your order so the better discount becomes available.
Finally, track your savings over time. Log each purchasing decision in a simple spreadsheet: date, supplier, pre-discount total, discount chosen, savings amount. After three months, you'll see patterns — which suppliers consistently offer better flat deals, which ones structure percentage promotions to look generous but save you less. That data becomes its own competitive advantage.
The whole workflow — from cart total to confirmed checkout — takes under a minute once you've practiced it. And every time you pick correctly, that's real margin preserved. Over a year of sourcing inventory, the difference between buyers who calculate and buyers who guess can amount to thousands of dollars.
Your supplies are discounted. Your thinking shouldn't be.