Discount Calculator
Calculate sale price, find discount %, and estimate real cost after cashback
Sale Price
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How to Use
This tool offers three modes. Switch between them using the tabs at the top — your inputs are preserved when you switch modes.
Sale Price mode: Enter the original price and the discount rate (%) to instantly see the discount amount and final sale price. Works for any "X% off" scenario.
Find Discount % mode: Enter the original price and the sale price to calculate the exact discount percentage. Useful when you see a before/after price and want to know the actual deal.
Cashback / Points mode: Enter the price, cashback (reward point) rate, and how many points you currently hold. The tool shows how many points you earn today and your effective out-of-pocket cost after spending your held points.
A note on terminology: "20% off" and "pay 80% of the original price" mean the same thing. However, "an 80% discount" is very different — it means 80% is removed, so you pay only 20%. Online retailers sometimes use ambiguous phrasing, so if a deal looks unusually large, use the Find Discount % mode with the actual before and after prices to verify.
How the Calculation Works
Sale Price: Discount amount = floor(original × rate ÷ 100). Sale price = original − discount. Rounding is always down (floor), which means the discount is never rounded up at the consumer's expense. Example: $1,000 at 20% off → floor(200.0) = $200 off → $800.
Find Discount %: Discount amount = original − sale price. Rate(%) = discount ÷ original × 100, rounded to one decimal place (Math.round(rate × 10) ÷ 10).
Cashback / Points: Points earned = floor(price × cashback rate ÷ 100). Effective cost = max(0, price − held points). Held points are treated as fully spent in this transaction. If your held points exceed the price, the effective cost is clamped to zero (never negative).
The real difference between cashback and an instant discount: 10% instant discount on a $1,000 item → you pay $900 and save $100 immediately (effective saving: 10%). 10% cashback on the same item → you pay $1,000 and receive 100 pts → you spend those points on a future purchase → effective saving = 100 ÷ (1,000 + 100) ≈ 9.1%. Any expiry date, minimum spend, or exclusion on the points program reduces the effective rate further. This tool assumes 1 pt = $1 and that all points are redeemable without restriction.
FAQ
- Is "20% off" the same as "paying 80% of the original price"?
- Yes, they are equivalent. "20% off" means you subtract 20% from the original price, so you pay the remaining 80%. Be careful with phrasing, though: "an 80% discount" means 80% is subtracted, leaving you paying only 20%. When in doubt, use the Find Discount % mode with the actual before and after prices to get the exact percentage instantly.
- Is 10% cashback better than a 10% discount?
- A straight 10% discount is slightly better. With 10% cashback on a $1,000 purchase, you earn 100 pts but still pay $1,000 upfront. When you redeem those points, the effective saving rate is about 9.1% (100 ÷ 1,100). Add an expiry date, a minimum spend requirement, or category restrictions on the points, and the real rate drops even further. That said, cashback programs can be nearly as good if you reliably spend every point you earn.
- When would I use the Find Discount % mode?
- Use it whenever you see a before-and-after price and want to check the real discount. Online retailers sometimes inflate the "original" price to make the sale look bigger than it is. Entering both prices here gives you the actual percentage immediately — handy for comparing deals across different stores or product categories.