Estimate
A planning range for cost, effort, or time based on what you know now, not a fixed promise of the final price.
See it
What it is
An estimate is a forecast of cost, effort, or duration based on what is known now. It is not a promise that the final number will land there. A useful estimate shows a range, its assumptions, what information is missing, and how uncertainty could move the result.
Reach for one early, when the client needs to test a budget or choose between approaches before the scope is firm enough to quote. Three-point estimation makes the uncertainty visible by recording optimistic, most likely, and pessimistic cases instead of pretending there is one magic number. It comes from PERT, built by the US Navy in 1958 to schedule the Polaris missile program, on the reasoning that nobody had built one before so nobody could honestly name a single date. Re-estimate after discovery or major scope changes.
Gotcha: clients remember the smallest number on the page. A single unqualified total gets treated like a quote even when the heading says 'estimate'. Pad for Hofstadter's Law, coined by Douglas Hofstadter in 1979: it always takes longer than you expect, even when you take into account Hofstadter's Law. Put the range and assumptions next to every total, include an expiry date, and say what event will produce a firm quote.
Ask AI for it
Estimate the project below using PERT three-point estimation. For every work package, give optimistic, most likely, and pessimistic hours, then calculate expected hours as `(O + 4M + P) / 6`. Convert the result to cost at the supplied rate, show low and high totals, list assumptions and unknowns, identify the three biggest uncertainty drivers, and state what discovery work would narrow the range. Label the output nonbinding and give it a 30-day validity window.