What is the formula for a discounted price?

Price × (1 − discount). For 20% off a $45 item: 45 × 0.8 = $36. The saving is 45 × 0.2 = $9.

How do I work out the discount percentage from two prices?

Divide the saving by the original price. $60 marked down to $48 saves $12, and 12 ÷ 60 = 0.2, so 20% off.

Is 20% off and then another 10% off the same as 30% off?

No. Stacked discounts multiply: 0.8 × 0.9 = 0.72, so you pay 72% of the price, which is 28% off, not 30%.

How to Calculate a Discount: 20% Off in One Step

How do you calculate a percent-off price?

October 27, 2026 · Avinash Kumar

Voice Calculator runs on iPhone. The app is available in English, Japanese, German, French, Spanish, Portuguese and Chinese.

Multiply the price by the share you still pay. 20% off means you pay 80%, so a $45 shirt costs 45 × 0.8 = $36. That one multiplication beats working out the saving and subtracting it.

What do you multiply by?

Discount	Multiply by	$45 becomes
10% off	0.9	$40.50
15% off	0.85	$38.25
20% off	0.8	$36.00
25% off	0.75	$33.75
30% off	0.7	$31.50
50% off	0.5	$22.50

How do you add sales tax after the discount?

Discount first, then tax. With 8% sales tax on the $36 shirt: 36 × 1.08 = $38.88. In most US states the tax is charged on the discounted price, but rules on coupons differ, so check your receipt.

What about “extra 10% off sale prices”?

Multiply both factors. 20% off and then an extra 10%: 45 × 0.8 × 0.9 = $32.40. That’s 28% off overall, a little less than the 30% the sign suggests.

Doing it by voice

I make Voice Calculator, so weigh this part accordingly. Standing in a store, you can say “45 times point 8 equals” and hear $36 read back. Every number lands on the tape, so you can see it heard “point 8” and not “8”. If you set your local rate in Settings, saying “plus tax” adds it to the total.

Questions people ask

What is the formula for a discounted price?: Price × (1 − discount). For 20% off a $45 item: 45 × 0.8 = $36. The saving is 45 × 0.2 = $9.
How do I work out the discount percentage from two prices?: Divide the saving by the original price. $60 marked down to $48 saves $12, and 12 ÷ 60 = 0.2, so 20% off.
Is 20% off and then another 10% off the same as 30% off?: No. Stacked discounts multiply: 0.8 × 0.9 = 0.72, so you pay 72% of the price, which is 28% off, not 30%.

Voice Calculator

A calculator you talk to: say the numbers, check each one on the tape, hear the total.

Download on the App Store