How to Use the Discount Calculator

The Tooldit Discount Calculator has three modes — pick the right tab at the top depending on the question you're actually trying to answer:

Find Sale Price — type the sticker price and the discount percent. The calculator returns what you'll pay, what you save, and (optionally) the post-tax total.
Find Original Price — when you only know the sale price and the percent off, this works the math backwards to reveal the pre-sale price.
Stack Discounts — add as many discounts as you want and the calculator applies them in order, showing each step and the true effective discount (which is always less than the naive sum).
Toggle Add sales tax in tab 1 to add your local rate. Tax is applied after the discount, the way most US retailers ring it up.
Hit Copy or Share to send the result to a friend before pulling the trigger on a deal.

Discount Calculation Formulas

All three modes are built on the same three formulas — useful to keep in your head when you don't have a calculator handy:

Sale Price = Original × (1 − Discount/100)

Savings = Original × (Discount/100)

Original Price = Sale Price ÷ (1 − Discount/100)

Stacked discounts are not additive. A 40% then 20% off promotion is not 60% off. Each percentage is applied to whatever the price has already been reduced to:

$100 × (1 − 0.40) = $60
$60 × (1 − 0.20) = $48
Total saved: $52 = 52% effective, not 60%.

Common Shopping Scenarios

Black Friday & Cyber Monday: typical 30–70% off; some categories (TVs, laptops) hit 60%+ on flagship promos
Clearance sales: 50–90% off, often triggered when seasons turn over or inventory needs to move
Member & loyalty discounts: 5–20% off, sometimes stackable with sale prices
Coupon codes: often a flat % off entire order, sometimes stackable with on-sale items
Buy-one-get-one (BOGO): "buy 1 get 1 free" = 50% off two items; "buy 2 get 1 free" = 33.3% off three
End-of-season clearance: 50–80% off in fashion as new collections arrive
Credit-card cashback: typically 1–5% — applied as a separate refund, not a price reduction
Student / military / senior discounts: usually 10–15%, often code-based, sometimes stackable with sale prices
Bulk purchase savings: 5–20% per-unit reduction on volume orders, common for office and household goods

Stacking Discounts — How it Really Works

The most common mistake in retail math is thinking you can addpercentages together. You can't. Each new discount is applied to the already-discounted price, so they compound the same way interest does — except in the customer's favour.

Worked example for a $100 item with 30%, 20%, and 10% stacked:

$100 → 30% off → $70
$70 → 20% off → $56
$56 → 10% off → $50.40

The naive sum says "30 + 20 + 10 = 60% off, so $40". The real effective discount is 49.6% — the customer saves $49.60 instead of $60. Stacked promos always save you less than the headline numbers suggest.

Order matters when discounts are mixed types. Two percentage discounts can be applied in either order with the same result (commutative). But if you mix percentage discounts with flat-dollar discounts, the order matters: $20 off then 10% off ≠ 10% off then $20 off. Most retailers apply percentage discounts first, then dollar coupons.

Sales Tax + Discounts

In the United States, sales tax is layered on top of the final discounted price — not the original — so you're only taxed on what you actually pay. Rates vary widely: 5 states have no statewide sales tax (Alaska, Delaware, Montana, New Hampshire, Oregon), while combined state + local rates can reach almost 10% in parts of Tennessee, Louisiana, Arkansas, and California.

A few states tax certain items differently — Pennsylvania and New Jersey don't tax most clothing, several states exempt groceries, and some have lower rates on prepared food. Online orders are taxed based on the shipping address (post-Wayfair ruling), not where the seller is located.

Finding Original Price from Sale Price

The reverse calculation matters whenever a deal claims "X% off!" without showing the original price. If the sale price is $60 and the tag says 40% off, the original was $60 ÷ (1 − 0.40) = $100.

This is also useful when you're double-checking a deal — comparing the "original" price the retailer claims against the actual sale percentage they're advertising. A fair number of stores inflate the "original" price ahead of a sale to make the discount look bigger; reverse- calculating from the sale price gives you a sanity check.

Frequently Asked Questions

+How are discounts and tax combined?

Sales tax is calculated on the post-discount price, the way most US retailers ring it up. So a $100 item at 30% off in a state with 8% sales tax: $100 → $70 (after discount) → $75.60 (after tax). The discount comes first, tax is layered on top.

+Can I stack multiple discount codes?

Whether stacking is allowed depends on the retailer's policy — some let you combine a sale price with a coupon code, some don't. The math itself works fine: each additional percentage is applied to the running total, not the original. Use the Stack Discounts tab to see what the final price would be if a retailer does honour all of them.

+How is 'buy 2 get 1 free' calculated?

You're paying for 2 of 3, so the per-unit price drops by a third — a 33.3% effective discount on the bundle. "Buy 1 get 1 free" (BOGO) is a 50% effective discount on the two items together. "Buy 3 get 1 free" is 25% off, and so on for "buy N get 1 free" where the discount is 1 ÷ (N + 1).

+Why isn't 50% + 25% off equal to 75%?

Because the second discount is applied to the already-discounted price, not the original. A $100 item with 50% off becomes $50; 25% off $50 is another $12.50, leaving $37.50. That's a 62.5% effective discount, not 75%. Stacked percentages always compound to less than the headline sum.

+How do I find the original price?

Use the Find Original Price tab. Enter what you're paying and the discount percentage, and the calculator divides by (1 − discount/100) to recover the original. Example: $60 sale price at 40% off → $60 ÷ 0.60 = $100 original.

+Is my data private?

Yes. The calculator runs entirely in your browser — prices, discount percentages, and tax rates never leave your device, aren't logged, and aren't tied to analytics. Refresh the page and the inputs are gone.

+Does it work offline?

Once the page is loaded, yes. The calculator runs entirely client-side, so subsequent calculations work without a network connection — handy for in-store comparison shopping where signal is patchy.