Reverse Percentage Calculator
Find the original whole number before a percentage share, tax markup, or discount with exact inverse arithmetic.
Reverse percentage
Reverse percentage formulas
Reverse percentage calculations solve for the initial 100% baseline when given a portion or adjusted value:
Standard reverse
When Y represents exactly P% of the unknown total whole.
Reverse tax / markup
When the total already includes an added percentage tax.
Worked examples with real numbers
50 is 20% of what?
Multiply: 50 × 100 = 5,000
Divide by 20: 5,000 ÷ 20 = 250
Original = 250
23 is 15% of what?
Multiply: 23 × 100 = 2,300
Divide by 15: 2,300 ÷ 15 = 153.33...
Original = 153.33
Price before 13% tax on $113
Divisor: 1 + 0.13 = 1.13
Divide: $113 ÷ 1.13 = $100
Original = $100.00
Frequently asked questions
How do you calculate the reverse percentage?
If you know that a number Y is P percent of an unknown base X, multiply Y by 100 and divide by P. Formula: Original = (Y × 100) ÷ P. For example, if 50 is 20% of a number: (50 × 100) ÷ 20 = 5000 ÷ 20 = 250.
How do you reverse calculate a price before sales tax or VAT?
Divide the final total price by (1 + Tax Rate ÷ 100). For example, if an item costs $113 with 13% tax included: $113 ÷ (1 + 0.13) = $113 ÷ 1.13 = $100 original pre-tax price.
How do you find the original price before a discount?
Divide the sale price by (1 − Discount Rate ÷ 100). For example, if a jacket on sale for $80 was discounted by 20%: $80 ÷ (1 − 0.20) = $80 ÷ 0.80 = $100 original price.
Related Calculators
Topically linked tools for related calculations and conversions.
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Calculate exact sales tax amount and total checkout price, or reverse calculate pre-tax price from a tax-inclusive total with step-by-step decimal arithmetic.
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Discount Calculator
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