Coupon Savings Calculator Formula
Understand the math behind the coupon savings calculator. Each variable explained with a worked example.
Formulas Used
You Save
you_save = discount_amtFinal Total
final_total = cart_total - discount_amtEffective Discount
effective_discount_pct = discount_amt / cart_total * 100Variables
| Variable | Description | Default |
|---|---|---|
cart_total | Cart Total(USD) | 85 |
coupon_type | Coupon Type | 1 |
coupon_value | Coupon Value | 15 |
discount_amt | Derived value= coupon_type == 1 ? cart_total * coupon_value / 100 : coupon_value | calculated |
How It Works
How Coupon Savings Are Calculated
Coupons come in two forms: a percentage off the total, or a fixed dollar amount. This calculator handles both and shows the effective discount rate.
Percentage Coupon
Savings = Cart Total x Coupon % / 100
Fixed Dollar Coupon
Savings = Coupon Dollar Amount
Worked Example
You have an $85 cart and a 15% off coupon.
- 01Coupon type: Percentage off
- 02Savings = $85.00 x 15 / 100 = $12.75
- 03Final total = $85.00 - $12.75 = $72.25
- 04Effective discount = 15.0%
Frequently Asked Questions
When is a fixed-dollar coupon better than a percentage coupon?
A fixed-dollar coupon is better when the discount amount exceeds what the percentage would save. For example, $20 off is better than 15% off on a $100 cart ($20 vs $15).
Can I use multiple coupons?
Most retailers allow only one coupon per order. If stacking is allowed, apply the percentage coupon first, then the fixed dollar amount for maximum savings.
Do coupons apply before or after tax?
Coupons reduce the pre-tax subtotal. Sales tax is then calculated on the reduced amount, so you also save a small amount on tax.
Ready to run the numbers?
Open Coupon Savings Calculator