Before You Run a Black Friday Deal, Do the Math

How many extra orders would make this discount worth it?

If you can answer that before your sale goes live, you are ahead of plenty of business owners who find out in January.

A discount feels generous. Your bank account sees it differently: a pay cut on every unit you sell. The good news is that the math fits on a napkin. Let’s walk through it.

Hypothetical example: Wick & Ember Candle Co.

Wick & Ember is a made-up shop. Its best seller is a large candle that normally sells for $40. The owner is considering 25% off for Black Friday weekend, which drops the price to $30.

Each candle carries $16 in variable costs: wax, jar, wick, fragrance, packaging, and card processing fees. Variable costs are the ones that show up every time you sell one more unit. Rent and salaries stay out of this, since you pay them either way.

On a normal weekend, the shop sells 50 of these candles.

The price fell 25%, but the dollars left per sale fell nearly 42%. That gap is the whole story. Every dollar of discount comes straight out of what you keep.

The math, one step at a time

Step 1: Find what a normal weekend leaves you after variable costs. 50 candles × $24 = $1,200

Step 2: Divide by the dollars left per sale at the sale price. $1,200 ÷ $14 = 85.71 candles

Step 3: Round up. Nobody buys 0.71 of a candle, and rounding down leaves you short. The target is 86.

Step 4: Double-check. 86 × $14 = $1,204, which clears $1,200. 85 × $14 = $1,190, which falls $10 short.

So the shop needs 36 more candles than usual, a 72% jump in units, just to tie a regular weekend. Not to win. To tie.

That answers the opening question. If you honestly expect 72% more volume, the sale could pay. If you’re hoping for 20% more, you’re paying customers to shop.

Extra costs raise the bar

Promotions rarely travel alone. They bring friends, and the friends send invoices.

One-time promo costs get added to the dollars you need to cover. Say the shop spends $300 on social ads and $200 on an extra part-time employee. That’s $500 more to earn back. ($1,200 + $500) ÷ $14 = 121.43, rounded up to 122 candles. Check: 122 × $14 = $1,708. At 121 candles, you’d have $1,694, short of $1,700.

Per-order costs shrink the dollars left per sale. Offer free shipping that costs $6 per order, and each sale now leaves $14 minus $6, or $8. (Assume one candle per order.) $1,200 ÷ $8 = 150 candles. That’s triple a normal weekend.

Stack the ads, staffing, and free shipping together and the target hits 213 candles. A modest-looking deal can quietly become a goal that needs a small miracle.

When a thinner margin still makes sense

Breaking even isn’t always the goal. Sometimes a promotion earns its keep in ways one weekend can’t show.

Clearing seasonal inventory. Holiday-scented candles get harder to sell every week after December. Taking $14 per unit now can beat holding stock that ties up cash and shelf space, then discounting it deeper in February.

Bringing in first-time customers. A discount can work as a paid introduction, but only if those customers come back at full price. Plan for that before the doors open: collect emails at checkout, or tuck a return-visit offer in the bag.

Either way, name the reason before the sale starts. “We’ll make it up later” only counts as a strategy if you know how.

Ways to protect your margins

You don’t have to choose between a deal and a profit. A few smarter structures help:

• Bundle products. Pair the candle with matches and a wick trimmer, then discount the set. Customers see a deal, and you earn on more items per order.
• Set a minimum purchase for perks. Free shipping on orders above a set amount spreads that shipping cost across a bigger sale.
• Limit discounts to select items. Put the deal on slow movers or high-margin products, not the best seller that sells itself at full price.
• Cap the quantity. A doorbuster on the first 30 units puts a ceiling on how much margin you give away.

Your pre-promotion checklist

Before you approve the deal, make sure you can check every box:

• ☐ I know my variable cost per unit, including packaging and payment fees.
• ☐ I know how many units I sell in a normal period of the same length.
• ☐ I calculated the dollars left per sale at the sale price.
• ☐ I added ads, staffing, and other promo costs to the target.
• ☐ I subtracted per-order costs, like free shipping, from the dollars left per sale.
• ☐ I rounded the required units up and double-checked the result.
• ☐ The required sales jump is realistic, not wishful.
• ☐ If the sale won’t break even, I can name exactly why it’s still worth running.

All checked? Run the sale with confidence. If not, tweak the deal until the math works for you, not just your customers.