Discount calculator
Reverse-calculate discounts from the discount rate, percentage reduction, or final unit price; use integer cents to calculate the quantity and discount deduction, and display the amount paid, savings, and effective discount rate.
How to use the discount calculator
Prices, quantities, and discounts are calculated only in the current browser and are not uploaded or recorded.
Enter the original price and quantity
Enter the original unit price and purchase quantity; amounts are first normalized to whole cents to avoid floating-point amount drift in individual items.
Choose a discount expression
You can enter a discount rate of 0–10, a reduction percentage of 0–100%, or work backward from a known final price to determine the effective discount rate.
Stack instant discounts and verify
Enter a fixed discount after the discount as needed; results show the actual amount paid per item and in total, savings, discount rate, and effective discount factor.
Limitations and Notes
- The calculation order is fixed: first apply the discount to the unit price, then apply a fixed reduction once to the total amount; it may differ from the merchant’s allocation, coupon thresholds, and rounding rules.
- The direct discount can reduce the amount paid to at most 0, without producing a negative price; shipping, taxes, points, cashback, bulk-item discounts, and refund allocation are outside the scope of the initial version.
- The page uses integer cents and integer basis points for calculations, but the final order is still subject to the merchant’s settlement page, coupon rules, and payment amount.
FAQ
Is paying eighty-five percent of the original price the same as subtracting 15%?
Without additional instant discounts or different rounding rules, both represent paying 85% of the original price.
Is the instant discount per item or for the entire order?
This tool always applies the additional reduction once to the discounted grand total, and clearly displays the calculation order in the results.
Can I work backward from the final price to calculate the discount?
Yes. After selecting the net unit price mode, the tool will calculate the effective discount multiplier and discount rate of that unit price relative to the original price.