Most marketing decisions are made without anyone modelling the outcome. This calculator does the arithmetic in the browser: nothing is sent anywhere, no email is required, and you can put whatever numbers you like into it.
How to use it honestly
Use your real figures, including the uncomfortable ones. Conversion rate means enquiries divided by sessions, not the number your last agency reported. Close rate means deals divided by enquiries. Average order value should be what you actually bill, not the premium package nobody buys.
What the output means
The model is deliberately simple: traffic times conversion rate times close rate times value, compared against cost. It ignores seasonality, lag and the compounding effect of organic work, all of which matter. Treat it as a sanity check on whether an investment could plausibly pay back, not as a forecast.
The number most people find surprising
Run the conversion rate scenario before the traffic one. Moving from two percent to three costs a fraction of doubling traffic and produces a similar result, permanently, on every channel at once. That is why conversion work is usually the first recommendation in an audit rather than the last.