How to Calculate a Discount When There Are Two Sales

Apply each percentage discount to the price left after the previous one. Twenty percent off followed by another 10% off makes a $100 item cost $72 before tax, an effective 28% discount. Adding the percentages would incorrectly predict a $70 price.

Follow the remaining price through checkout

An additional percentage offer usually describes a reduction from an already reduced price, if the store permits the combination. The original price is not the base for every discount. Write down the price at each stage instead of adding percentages shown on different signs.

For a single discount, multiply original price by one minus the discount written as a decimal. A 20% discount leaves 80% to pay, so the remaining-price factor is 0.80. An additional 10% leaves 90% of that remaining amount, giving a second factor of 0.90.

The Discount Calculator supports two sequential percentages, optional tax and a reverse direction. It cannot decide whether a particular coupon qualifies; check that the combination is allowed before treating the arithmetic as a checkout prediction.

Calculate the second saving from the reduced amount

Let P be original price, d1 the first percentage and d2 the additional percentage:

Price after first discount = P × (1 − d1/100)
Final price before tax = P × (1 − d1/100) × (1 − d2/100)
Total savings before tax = P − final price before tax

For the $100 example, 20% off saves $20 and leaves $80. The second 10% saves $8, not $10, because it applies to $80. The combined saving is $28 and the remaining price is $72.

This makes a useful receipt check: if the store shows two separate savings lines, compare the second line with the price immediately before it. A second $10 reduction would instead be a fixed-dollar coupon or a percentage applied under different rules.

Express both discounts as one effective percentage

The effective combined discount compares the final before-tax price with the original:

Effective discount % = [1 − (1 − d1/100) × (1 − d2/100)] × 100

With 20% and 10%, the remaining share is 0.80 × 0.90 = 0.72. The discount is therefore 1 − 0.72 = 0.28, or 28%. It falls short of 30% because the second discount no longer applies to the part already removed.

Use the effective percentage when comparing this eligible offer with a single discount on the same original price. Also compare the actual final dollars: two stores can advertise different percentages while starting from different prices.

Check several common shopping combinations

The prices and tax rate below are hypothetical examples, not advertised sales or claimed market prices.

Original price	First discount	Additional discount	Before-tax price	Effective discount
$100	20%	10%	$72.00	28%
$80	25%	15%	$51.00	36.25%
$120	30%	20%	$67.20	44%
$50	50%	50%	$12.50	75%

For the $80 item, the first reduction leaves $60. Fifteen percent of $60 is $9, leaving $51. Savings are $29, and $29 ÷ $80 × 100 = 36.25%.

Two 50% reductions do not make an item free: the first halves it to $25 and the second halves that to $12.50. Each stage reduces what remains. A full 100% discount is different because its remaining-price factor is zero.

When does discount order matter?

For two unrestricted percentages applied to the same eligible price, changing their order does not change the unrounded mathematical result. Multiplication gives $100 × 0.80 × 0.90 = $100 × 0.90 × 0.80.

That does not mean all coupons can be rearranged. A fixed $10 coupon and a 20% reduction demonstrate why. Starting from $100, subtracting $10 first gives $90, then $72 after 20% off. Applying 20% first gives $80, then $70 after subtracting $10. Different rules produce different dollar totals.

Eligibility can also depend on minimum spend, excluded items, coupon caps or whether a threshold is evaluated before other offers. Read the actual terms. Jolbox’s two discount fields are percentages; entering 10 in the second field means 10%, not a $10 coupon.

Stores may round intermediate stages to cents. The calculator keeps precision until display, so a real receipt can differ slightly under its own rounding rules. For example, $19.99 reduced by 15% and then 10% is $15.29235 before final rounding, displayed as $15.29.

Keep sales tax separate from discount savings

If an illustrative 5% tax applies to the full $72 discounted amount, tax is $3.60 and the amount after tax is $75.60. The $28 discount saving still compares original price with discounted price before tax.

Actual tax treatment can depend on the transaction and applicable rules. Use the checkout’s correct taxable basis and rate instead of assuming every coupon changes tax in the same way. The calculator applies one entered flat rate to its entire discounted price and does not determine eligibility, exemptions or local rules.

Shipping and other fees are also outside that simple percentage comparison. A lower product price does not guarantee a lower delivered total. Keep those amounts visible when comparing offers or planning a grocery budget.

Recover an original price from a sale price

To reverse two known percentages, divide the before-tax sale price by both remaining-price factors:

Original price = sale price before tax
                 ÷ [(1 − d1/100) × (1 − d2/100)]

A $51 sale price after 25% and 15% off implies $51 ÷ (0.75 × 0.85) = $80 originally. Dividing by 0.60, as though the discounts added to 40%, would give $85 and answer a different question.

If the only available amount is tax-inclusive, first remove a known simple tax factor when that assumption fits. For the earlier example, $75.60 ÷ 1.05 = $72, then $72 ÷ 0.72 = $100. Unknown fees or different tax treatment prevent that shortcut from being reliable.

A 100% discount cannot be reversed to a unique original price: every original amount becomes zero. For ordinary offers, keep the original price, eligible discounts, tax basis and fees recorded separately so the final comparison can be checked.