What is an S-curve in project management?

An S-curve is a graph that plots a cumulative value — progress, cost, hours or earned value — against time. Its characteristic S shape reflects the slow start, rapid middle and tapering end of most projects.

Why the S shape

Projects ramp up slowly as they mobilise, accelerate once execution is in full swing, then slow down again during finalisation and closure. Plotting cumulative effort over time naturally produces the S.

What it is used for

Comparing the planned (baseline) S-curve with the actual one shows at a glance whether a project is ahead, on track or behind — on schedule, on budget or on effort. The gap between the two curves quantifies the deviation.

Types of S-curve

Common variants track cost, man-hours, physical progress or earned value. In earned value management, comparing planned value, earned value and actual cost curves reveals both schedule and cost performance.

S-curves in FoxPlan

FoxPlan compares planned vs. actual in real time across schedule, cost and progress — turning raw project data into the trend view a manager needs to spot drift early.