Percentage off
Multiply the original price by the discount percentage to find the saving, then subtract it from the original price.
Sequential discounts
Two successive discounts apply to different starting amounts. A further 10% after 20% off produces 28% total reduction, not 30%.
Multi-buy offers
Convert the offer to a per-item or per-unit price and compare it with the normal price. The saving matters only if all items will be used.
Practical checklist
- Compare against the genuine normal price.
- Separate loyalty rewards from immediate cash savings.