Ecom Profit & Scale Planner: Break-Even ROAS, Ad Spend Scaling & Black Friday Offer Calculator (Offline HTML)

"Our ROAS is 3. Should we scale?" You can only answer that once you know your contribution margin, and most store owners don't.

Ecom Profit & Scale Planner is a single HTML file that opens in any browser and runs fully offline. It takes you from one average order to a full scaling plan in about 10 minutes.

What it calculates

• Unit economics: contribution per order after product cost, shipping, packaging, payment and platform fees, VAT and refunds. Includes a visual waterfall of where each order's money goes.
• Break-even and target ROAS / CPA, on the revenue basis your ad dashboard actually uses.
• Scale planner: profit at every ad-spend level, modelling the fact that CPA rises as you spend more. Shows the profit-maximising spend, the marginal CPA your last dollars are buying, the spend at which ads stop paying, and the spend needed to cover fixed costs. Includes a 90-day repeat-purchase view.
• Offers & BFCM: compare up to 4 promotions (% off, fixed amount off, free shipping, free gift). See the contribution left per order and how many extra orders each offer needs just to break even.
• Payback & LTV: first-order profit, 12-month contribution per customer, LTV:CAC, and orders needed to pay back acquisition.

Built for real use

• Works offline and makes no network requests. No account, no subscription, and your numbers never leave your device.
• Any currency, with VAT-inclusive pricing for EU, UK and AU sellers.
• Save named scenarios, export/import JSON, export CSV for Sheets or Excel, and print a clean PDF report.
• Mobile-friendly, with input validation on every field.
• Includes a 3-page Quick-Start PDF showing where to find each number in Shopify, plus an example scenario.

Who it's for: Shopify and DTC store owners, Etsy and TikTok Shop sellers running ads, media buyers and freelance ecommerce consultants preparing client plans.

Honest notes

• This is a planning model, not accounting software. The CPA-vs-spend curve is a simplification, so re-measure monthly. It does not model inventory cash flow, chargebacks or income tax. It is not financial or tax advice.
• Fees are editable inputs, not hard-coded, because they differ by country and plan.
• Made with AI assistance. The formulas were derived and checked by hand and verified by an automated test suite (58 checks against an independent reference calculation).

What you get: Ecom-Profit-Scale-Planner.html, the Quick-Start PDF and Markdown, example-scenario.json, README and licence (use for your own stores and your clients' stores; no redistribution).