Mark Hay
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Live Tool Suite·2026·Live

E-Commerce Utility Calculators

A compact suite of focused calculators built to answer the commercial arithmetic questions that come up repeatedly in e-commerce: true per-unit profit on TikTok Shop, the fee tipping-point between Etsy and Shopify, and the real landed cost of importing goods into the UK.

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The problem

E-commerce sellers spend a lot of time doing margin calculations on the back of envelopes, in spreadsheet cells, or in their heads. The numbers involved are not complicated — but there are enough variables, platform-specific fee structures, and tax rules involved that getting to the right answer quickly is genuinely harder than it should be.

TikTok Shop has its own commission model, affiliate fee logic, and ad spend dynamics that a standard gross margin formula does not capture. The Etsy vs Shopify question comes up every time a seller starts to scale — but the maths changes depending on volume, and most sellers guess rather than calculate. UK import duty is structured in a way that surprises importers: VAT is charged on the duty-inclusive value, not the goods value alone.

These are narrow, specific problems. They do not need a platform. They need a calculator that gets the arithmetic right and returns an answer immediately.

What it does

  • TikTok Shop ROAS Calculator — enter cost price, sale price, fees, and ad spend to get true per-unit profit and break-even ROAS in one step
  • Shopify vs Etsy Comparator — model the exact monthly revenue point where Shopify subscription fees become cheaper than Etsy listing and transaction costs
  • UK Import Duty & VAT Calculator — enter product value, commodity code duty rate, and shipping costs to get a clear landed cost and total tax exposure
  • Currency selector for cross-border calculations, with common e-commerce currencies pre-loaded
  • Mobile-first layout designed for quick in-context use — when you need the number, you need it now
  • No login, no account, no data stored — open and use instantly

Product choices

The decisions that shaped this as a decision tool rather than a generic number cruncher.

01

Narrow scope, deep accuracy

Each calculator focuses on one specific decision and handles it correctly. The TikTok Shop calculator accounts for platform fees, affiliate commissions, and ad spend in a way a generic margin tool does not. Depth over breadth.

02

Decision-first output

The output is framed as an answer to a decision, not just a number. Break-even ROAS tells you the floor you must beat. The Shopify tipping-point tells you when to switch. The landed cost tells you whether the margin survives the import.

03

No friction — no account required

Most financial tools want an email address before they show you anything. This does not. Open it, enter numbers, get an answer. The absence of onboarding is a deliberate product choice.

04

UK import compliance built in

The import duty calculator is structured around the UK tariff schedule and HMRC VAT rules. It accounts for duty on the full CIF value (cost, insurance, freight), then applies VAT on top of that — which is how HMRC calculates it, and not how most importers first assume it works.

Scope boundaries — and why

The things that were deliberately left out, and the reasoning behind each decision.

No saved scenariosThere is no ability to save or compare multiple product scenarios side by side. For a quick decision tool, this is acceptable friction. A saved-scenario layer would require accounts, storage, and session logic — scope that the tool does not need to be useful.
Static duty ratesUK tariff rates are entered manually rather than pulled from a live commodity code lookup. Rates do change, but not frequently. For the decision-support use case — should I import this product? — manual input is accurate enough and avoids the complexity and maintenance of a live tariff API.
TikTok Shop fees as inputs, not a live lookupTikTok Shop commission rates vary by category and change as the platform matures. The calculator accepts the current applicable rate as an input, so it stays accurate regardless of platform changes without needing an API dependency.
No multi-currency conversionThe currency selector changes the display symbol only — it does not convert between currencies. Cross-currency margin calculations add a layer of FX risk modelling that goes beyond the tool's scope. The intent is to calculate within a chosen currency, not to model hedging.

What worked

  • The TikTok Shop calculator produces answers that are genuinely surprising — most sellers underestimate the combined impact of platform fees and ad spend on per-unit margin
  • The Shopify vs Etsy tipping-point is a real decision that e-commerce sellers face, and the calculator makes it concrete rather than rule-of-thumb
  • The UK import duty structure correctly models the HMRC calculation order, which differs from the common assumption
  • No-login design removes the biggest drop-off point for utility tools

Natural next steps

  • Amazon FBA calculator as a fourth module — fulfilment fees, referral fees, and FBA pick-and-pack are a well-understood pain point
  • Scenario comparison — save two versions of the same calculation and compare them side by side
  • Printable or shareable output for quoting landed costs to clients or suppliers
  • TikTok Shop fee category lookup to remove the manual rate input step

Try the calculators

No login required. Open the tool, enter your numbers, and get an answer. TikTok Shop ROAS, Shopify vs Etsy tipping-point, and UK landed cost — all in one place.

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