How accurate is this calculator?
Honest answer: directionally accurate within ~15-25% for the median case in each GMV bracket, less accurate at the extremes. It’s a first-pass screening tool, not a procurement-grade quote.
What it gets right:
- License tier ordering. Magento Open Source $0 vs Adobe Commerce $30k, $150k+ vs SFCC $200k+, the ranking won’t change.
- Per-tx fee impact at scale. Shopify Plus 0.15% adds up identically every time; the math is exact.
- Dev cost order of magnitude. A $5M GMV store on Magento needs ~$40k upfront + $30k/yr ongoing, the bracket holds across most engagements I’ve seen.
Where it’s less accurate:
- SFCC and Adobe Commerce license, both are negotiated. Tier-1 SI partners often hold ±30% pricing power. The calculator uses public list-equivalent ranges; your actual quote may be lower (negotiated) or higher (uplift for Adobe Commerce Cloud Pro vs Starter).
- Custom dev edge cases, if your scope includes headless commerce, ERP integration, or multi-region inventory orchestration, dev cost can be 2-3x the calculator’s number.
- Region-specific pricing, the model assumes US dev rates. EU SI partners run 0.7-0.9x; India / Eastern Europe freelancers run 0.3-0.5x; Tier-1 US/UK SIs can run 1.2-1.5x.
Use it to rule out platforms and frame the conversation, not to write a budget line.