The calculator adds up costs month by month, out to month 120, for two paths: keep paying for your subscriptions, or build custom software to replace them. Results appear once you’ve entered one priced subscription, a build cost, months to launch and yearly maintenance. Other blank boxes count as zero.
Per subscription: s = seats, q = price per seat per month, F = platform fee per month. g = seat growth and pi = price increase per year, applied from year 2. I = one-time setup or migration, A = add-ons, integrations and admin per year, W_buy and W_build = workaround hours per month with the subscriptions and after launch, r = loaded hourly cost for both paths, B = build cost, L = months to launch (whole months), Hst = hosting and M = maintenance per year, Y = years to compare.
Overlap, break-even and sensitivity
The overlap box (“We keep paying for the subscriptions while the build is underway”) starts ticked, since your team still needs the old tools until launch. Break-even counts only months after launch and is the first crossing; one after your horizon is labeled that way. If the build is back above the subscriptions by the end of your horizon, the results card warns you.
Cost per seat puts your per-seat SaaS cost next to the build’s in the last month of year Y, with seats summed across tools. Break-even seats scale every tool’s seats together, growth and prices unchanged: “0 seats” means the build costs less even without per-seat charges, and “Not reached” means no seat count closes the gap. The sensitivity table reruns everything with price increase at 0%, seat growth at 0%, and maintenance at 75% and 125% of your figure.
Worked example (hypothetical)
Example (hypothetical): the round numbers the “Try a hypothetical example” button loads. They’re not client data, typical prices, benchmarks or EP prices. Subscriptions: a work-order app at 60 seats × $45 a month and a scheduling add-on at 60 seats × $15 a month plus a $200 monthly fee, 5% seat growth, 0% price increase, $5,000 one-time setup, $6,000 a year in add-ons and 40 workaround hours a month at $40 an hour. Build: $100,000 over 6 months, $3,600 a year hosting, $15,000 a year maintenance and 5 workaround hours a month after launch. Compared over 5 years.
Year-5 cost per seat per month: $45.77 for the subscriptions, $12.00 for the build. Break-even seats: about 36, against 120 entered. In the sensitivity table, break-even stays at month 29 with 0% price increase (“same as yours”) and 0% seat growth, and moves to month 27 with maintenance 25% lower and month 30 with it 25% higher. Untick the overlap box and it moves to month 21.
Assumptions and limits
- Plain running totals: no discounting, tax or depreciation.
- The build cost is spread evenly up to launch. If launch falls at or after the end of your horizon, the card warns that the totals are incomplete.
- After launch the build path pays no subscriptions, so it assumes every tool you list is replaced. For a hybrid, list only the tools the build would replace.
- Money, seats and hours can’t go below zero; seat growth and price increase accept −99% to 500%.