Discount Percentage Calculator: % Off, Reverse, Volume

Discount math, both directions

Every discount question is one of two: "what percent off is this?" (two prices, find the rate) or "what will I pay?" (price and rate, find the total). This calculator does both side by side: no switching modes, no formula lookup. Type, read, done.

The formulas

Discount % = (original − sale) ÷ original × 100. A $80 item at $60 is 25% off. Final price = original × (1 − discount%). A $120 item at 25% off is $90. The mirror-image trap: 25% off then 25% back on does not return to the original: $120 → $90 → $112.50, because the percentage bases differ.

Stacked discounts never add

"Extra 10% off already-reduced items" applies to the reduced price. 20% + 10% = 28% total; 50% + 30% = 65%, not 80%. Retailers rely on shoppers adding the numbers. To stack: multiply the remainders: (1−0.20) × (1−0.10) = 0.72, so 28% off.

For sellers: discount vs. margin

A 20% discount usually costs far more than 20% of profit. Selling at $100 with a 40% margin, a 20% discount cuts profit in half: you need 50% more volume just to stay even. Before a sale, check the real cost against your bulk discount tiers or run your margins in the wholesale price calculator. Setting prices from cost? Use the contractor markup calculator or the 40% markup shortcut. Discounting is marketing spend by another name; the same test applies, which is whether the extra volume covers the margin given away. The return on marketing spend guide works through that arithmetic.

Where discount calculations break in practice

The most common error is applying a percentage to the wrong base. A $200 item marked down to $150 is a 25% discount - calculated as (200 − 150) ÷ 200 × 100. Dividing the savings by the sale price instead gives 33.3%, which overstates the deal. Retailers sometimes publish the latter figure deliberately; knowing the difference lets you verify claims instantly.

Percentage-off figures also break when the listed "original" price is inflated. The FTC's Guides Against Deceptive Pricing require that a reference price reflect a bona fide former price at which the item actually sold, offered in good faith for a reasonable, substantial period of time - generally interpreted as at least 28 consecutive days at that price within the preceding 90 days. A discount calculated against a fictitious original is legally a deceptive practice, not just a math error.

Rounding direction matters at scale. A 0.5% rounding difference on a $5,000 invoice is $25. Rounding mid-calculation - rather than rounding only the final result - compounds this. Always carry at least four decimal places through intermediate steps and round once at the end.

Discount tiers and volume pricing benchmarks

Standard B2B volume discount tiers in wholesale distribution run roughly 5% at 10–24 units, 10% at 25–49 units, 15% at 50–99 units, and 20%+ at 100 units. These are starting benchmarks, not rules - commodity categories compress margins and often cap at 8–12% even at high volume. The wholesale price calculator handles the layered arithmetic when multiple tier thresholds apply within a single order.

Prompt-pay discounts follow a separate convention. 2/10 net 30 means a 2% discount if payment arrives within 10 days against a 30-day terms invoice. Annualized, that 2% over 20 days is equivalent to roughly 36.5% APR - a meaningful incentive. Calculating whether to take it requires comparing that implied rate against your cost of capital, not just noting the headline percentage.

What this calculator does not cover

This tool computes the discount percentage between two prices, or the sale price from a percentage and original price. It does not account for sales tax applied post-discount versus pre-discount, which affects the tax base differently depending on jurisdiction. In most US states, sales tax applies to the final discounted price; in a handful of cases, coupon type (manufacturer versus store) changes the taxable amount. The tool also does not model rebate structures, where the purchase price is paid in full and a portion returned later - the effective discount is identical mathematically, but cash-flow timing and accounting treatment differ.

For contractor pricing that layers markup on top of a discounted material cost, the contractor markup calculator separates those two operations correctly. Running markup and discount as a single percentage produces a distorted margin figure - a 20% discount followed by a 25% markup does not net to 5%; the actual margin on original cost is exactly 0% before overhead.