Calculator
Example data table
| Scenario | Cart setup | Coupon | Key outcome |
|---|---|---|---|
| Percent discount | $40 × 2, shipping $6, tax 8% | 15% off merchandise | Saves about $12.00 before tax changes |
| Fixed discount | $25 × 3, shipping $5, tax 7% | $10 off order, cap $10 | Exactly $10.00 off when eligible |
| Free shipping | $60 × 1, shipping $12, tax 0% | Shipping waived | Saves the full $12.00 delivery charge |
| BOGO deal | $30 × 4, shipping $0, tax 5% | Buy 1 get 1 free | Two items discounted to $0.00 |
| Tiered discount | $55 × 2, shipping $8, tax 10% | 10% off at $100+ subtotal | Tier triggers when subtotal reaches threshold |
Use “Load Example” to try one setup instantly.
Formula used
- Merchandise Subtotal = Unit Price × Quantity
- Discount Base = Subtotal (or Subtotal + Shipping if selected)
- Percent Discount = Discount Base × (Percent ÷ 100)
- Fixed Discount = Amount (or Amount × Quantity if “per item”)
- BOGO Discounted Items are computed per buy/get cycle, then discounted by Percent
- Tiered Percent is chosen from the highest eligible tier
- Discount Cap scales discounts if the total exceeds the cap
- Tax = Taxable Base × (Tax Rate ÷ 100) (taxable base depends on selected rules)
- Final Total = (Subtotal − Discounts) + (Shipping − Shipping Discounts) + Tax − Gift Card
How to use this calculator
- Enter unit price, quantity, shipping, and your estimated tax rate.
- Select a coupon type and fill its value (percent or amount).
- Set optional limits like minimum order and maximum discount cap.
- Choose tax rules: apply coupon before tax and whether shipping is taxed.
- Click Calculate Savings to view results above the form.
- Use the CSV or PDF buttons to export the breakdown.
Coupon types and what “value” means
Percentage coupons reduce a chosen base by a rate, such as 15%. Fixed coupons subtract a money amount, either once per order or per item. Free‑shipping coupons remove delivery charges, sometimes with a cap. BOGO coupons discount a set of “get” items by a chosen percent. Tiered coupons apply the best rate once a spend threshold is met.
Shipping and tax can change the real savings
Two carts with the same discount can produce different totals when tax and shipping rules differ. If a coupon applies before tax, the taxable base is smaller and tax drops too. If it applies after tax, the discount lowers only the payable amount. Shipping may be taxable in some regions. The calculator lets you toggle both rules to see their combined impact. For example, a 10% coupon on a $120 cart with $10 shipping saves $12 on merchandise only, but $13 when shipping is included, before any tax differences are applied in your selected ruleset.
Minimum order and discount caps protect margins
Many promotions require a minimum merchandise subtotal, like $50, before any discount activates. Caps limit the total discount, such as “up to $25 off,” preventing extreme reductions on large carts. When a cap is hit, the calculator scales discounts proportionally across merchandise and shipping when your coupon applies to the total. This mirrors how many checkout systems allocate savings.
BOGO math depends on cart quantity
For “buy X, get Y,” discounts repeat in cycles. With buy 1 get 1, a quantity of 4 creates two discounted items; a quantity of 3 discounts only one. If the “get” items are 50% off, only half their value is reduced. Use the BOGO fields to match your deal wording and avoid assuming every extra item is free.
Use exports to compare offers consistently
When you test multiple coupons, consistent reporting matters. Export the CSV to compare effective discount rate, total discount, and final payable across scenarios. Export the PDF for a shareable snapshot with timestamps and coupon identifiers. Keeping these records helps teams validate campaign performance, estimate customer savings, and spot policies like exclusions or caps that change outcomes.
FAQs
How do I model a free shipping coupon?
Choose “Free shipping” and enter an optional cap. Use 0 to waive the full shipping charge. If your store also discounts merchandise, run a second scenario using a percent or fixed coupon and compare totals.
Should I apply the coupon before or after tax?
Match the checkout you use. Many systems discount first, then compute tax on the reduced taxable amount. If your receipt shows tax based on the pre-discount price, uncheck “Apply coupon before tax” to mirror that behavior.
Why is “savings vs no coupon” different from “total discount”?
Savings compares final payable totals, including how tax and gift cards change. A coupon can reduce tax when applied before tax, increasing savings. A gift card may reduce both scenarios similarly, narrowing the savings difference.
How does the BOGO calculation work for odd quantities?
The tool counts full buy/get cycles, then checks the remainder. For buy 1 get 1, quantity 3 discounts one item, while quantity 4 discounts two. Adjust X, Y, and percent to match your promotion terms.
What happens when a maximum discount cap is set?
If the computed discount exceeds the cap, the calculator scales it down to the cap value. When discounts apply to merchandise plus shipping, the reduction is allocated proportionally so neither component is discounted beyond its available amount.
Can I include store credit or a gift card?
Yes. Enter the credit in “Gift card / store credit.” It is applied after tax in this calculator, which matches many checkouts. If your platform applies credit before tax, treat the output as an estimate and compare with receipts.