StackLab

Worldwide · Private

Free · No signup · Private

Stacked Discounts & Margin Hit

Stack percent-offs the way checkout really works (multiplicative), compare to naive “add the %s”, see final price, and measure how hard the stack hits your margin. Educational only — not a promo engine.

Stack discounts

True stack Vs additive Final price Margin hit 40+ currencies

Display currency

Works worldwide. Changes money labels only, not a live FX converter.

ActiveUSD

Quick picks

1. Search by continent

2. Search country or currency

3. Sort + country filter

Country filter

4. Countries / currencies

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Display currency for money

USD

Shortcuts: 1–4 switch tools · c copy · p print · s share

True stack (multiplicative)

Each discount applies to what’s left. Leave D3 at 0 for a double stack. Optional fixed $ off after percents.

List / start price Discount 1 % Discount 2 % Discount 3 % (optional) Extra fixed $ off

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Enter price and discounts.

Stacked vs additive

Naive add = sum of %s (capped at 100%). True stack multiplies. Gap = how much “free” discount people assume.

List / start price Discount 1 % Discount 2 % Discount 3 %

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Enter price and stack percents.

Final customer price

Full path: list → % stack → fixed off → optional tax/VAT on the discounted price (display only).

List price Discount 1 % Discount 2 % Discount 3 % Fixed $ off Tax / VAT % on final (optional)

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Enter list price and discounts.

Margin hit

Compare margin at list vs after true stack. Cost is your unit cost (COGS). Margin % = (price − cost) ÷ price.

List price Your cost / unit Discount 1 % Discount 2 % Discount 3 % Fixed $ off

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Enter list, cost, and discounts.

Single coupon / code

Percent off, fixed off, or both (percent first, then fixed). Optional min subtotal.

Subtotal Percent off Fixed off $

Gate

Min subtotal to apply

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Enter subtotal and coupon.

Buy X get Y free

Effective unit price = (pay-for count × price) ÷ total units received.

Unit list price Buy (pay for) Get free

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Enter price and BOGO counts.

Volume tier discount

If qty ≥ threshold use tier % off, else base %. Simple two-tier model.

Unit price Quantity Tier starts at qty Base % off Tier % off

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Enter price, qty, tiers.

Dollars saved vs list

Saved = list − final pay.

List price Final pay

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Enter list and final.

Multi-buy total

Total = unit price × qty after % off.

Unit price Qty % off

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Enter price, qty, % off.

Price after stacked % off

Final = list × (1 − d1) × (1 − d2).

List price Discount 1 % Discount 2 %

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Enter list and discounts.

How StackLab works

People often “add” promo percents. Carts usually don’t.

True stack: price × (1−d1) × (1−d2) × (1−d3) − fixed.
Additive: price × (1 − min(1, d1+d2+d3)).
Final price: stack path + optional tax on discounted amount.
Margin hit: list margin vs post-stack margin and $ profit change.
Coupon: one % and/or fixed code → pay price (optional min).
BOGO: buy X get Y free → effective unit price.
Tier discount: qty threshold switches base vs tier % off.
$ saved: list − final pay.
Multi-buy: unit × qty after % off.
Price after disc: list × (1−d1) × (1−d2).

Pair with MarginLab, Seller fees, InvoiceLab. Not legal promo or pricing advice.

FAQ

Why isn’t 20% + 10% = 30% off?

After 20% off $100 you have $80; 10% of $80 is $8, so you pay $72 — 28% effective, not 30%.

Order of discounts?

StackLab applies D1 then D2 then D3 left-to-right on the remaining price, then fixed $ off. Real carts may order differently — match your platform.

Live FX?

No. Currency only relabels amounts.

Why is 20% off then 10% off not 30% off?

Each percent applies to the remaining price. 100 then 20% is 80; then 10% is 72, which is 28% effective, not 30%.

Does discount order change the result?

For pure percent stacks, multiplicative order yields the same final percent. Fixed dollar off after percents can depend on order — match your cart rules.

Should I stack sitewide and coupon codes?

Only if your cart rules allow it. If they stack, use multiplicative math here so finance and marketing agree on the real discount.

How do stacked discounts affect margin?

Each extra percent cuts price and contribution. Check margin after the full stack before you approve a campaign.

Do BOGO and percent-off stack the same way?

No. BOGO is a different mechanic than sequential percent-off. This tool focuses on percent stacks — model BOGO as an effective percent if needed.

How do I explain effective discount to a client or boss?

Show the step-down price: after each percent, then the combined effective percent. That beats arguing 20+10=30 when the cart charges 28% off.