The Planning Fallacy

Plans often underestimate real-world work.

On this page

01 / UNDERSTAND

The idea

People can underestimate the time or resources a task requires when imagining a smooth path. Use observed completion data, dependencies and ranges rather than optimistic guesses alone.

People can plan around an optimistic, uninterrupted version of a task, even when they know estimates are often wrong. A flow that lasts longer than expected can lead to abandonment or rushed answers. Set realistic expectations before starting and update them when conditions change. Distinguish active work from external waiting.

02 / RECOGNISE

See it in real products.

Examples of how the principle can appear in an interface.

WeBullEXAMPLE 01

Give useful remaining-work context

WeBull’s exit prompt explains the effort still required. A credible estimate helps someone decide whether to continue rather than leaving them with a vague progress signal.

UberEXAMPLE 02

Keep expectations current while waiting

Uber’s timed waiting example resets expectations during a delay. The timing needs to reflect real conditions and communicate changes rather than repeatedly implying completion is imminent.

03 / CONNECT

Why it matters.

An unexpectedly long task can prompt abandonment, frustration or rushed answers. Set realistic expectations and update them when the situation changes.

Possible influences to investigate, rather than guaranteed outcomes for every product.

04 / APPLY