About the Discount Calculator

What it does

Computes sale price, savings, and final checkout total from a list price and discounts. Supports single or stacked discounts, coupons, tax, and quantity.

Fields in this calculator

• Original price: List price before any discount or tax.
• Discount (%): Percentage off the original price. You can enter multiple discounts if supported.
• Coupon / Fixed off (optional): Flat amount subtracted after percentage discounts.
• Tax (%) (optional): Sales/VAT applied after discounts (jurisdictions vary).
• Quantity (optional): Number of units purchased.
• Shipping/Fees (optional): Added at the end if applicable.

Core formulas

Single discount:
  Sale = P × (1 − d)
Stacked discounts (d1, d2, ... as decimals):
  Sale = P × (1 − d1) × (1 − d2) × ...
Coupon (flat C applied after %):
  Sale_net = max(0, Sale − C)
Tax t%:
  Final_unit = Sale_net × (1 + t)
Quantity q and fees F:
  Final_total = Final_unit × q + F
Savings:
  Savings = P × q − (Final_total − F)
Effective total % off (before tax/fees):
  Eff% = 1 − (Sale_net / P)
Reverse: given final price FP and P, single d:
  d = 1 − (FP / P)
      

Outputs

• Sale price (per unit): After all discounts and coupons, before tax.
• Final price (per unit): After tax.
• Total: Final price × quantity + shipping/fees.
• Total savings: Money saved versus original price × quantity.
• Effective discount: Net percentage off the original price.

Notes and edge cases

• Stacked percentages multiply, they do not add. 20% then 10% ≠ 30%; it equals 28% effective.
• Some stores apply tax before coupons; toggle method if your region requires that.
• Minimum advertised price rules may cap coupon use; clamp at zero if discounts exceed price.
• Rounding can occur at line or cart level; totals may differ by a few cents.

Use it well

• Compare “effective % off” across deals for a fair comparison.
• Include shipping and tax to see true checkout cost.
• For bulk deals, test different quantities to catch threshold promotions.

Informational tool. Store rules, tax law, and rounding policies vary by location and merchant.