A value stream map (VSM) is a Lean diagram that captures every process step, inventory buffer and information flow between raw material and the finished product reaching the customer. Unlike a flowchart, a VSM carries data — cycle time, changeover, uptime, inventory — so you can see not just what happens, but how long the work waits.
The two clocks
Every VSM tracks two very different clocks. Value-add time is the hands-on work that changes the product. Lead time is the total elapsed time, most of which is usually waiting in inventory. The gap between them is where waste hides — and Process Cycle Efficiency (value-add ÷ lead time) puts a number on it.
Takt time sets the pace
Takt time is your available working time divided by customer demand — the pace at which one unit must be completed to keep up. Any process whose cycle time is slower than Takt is a bottleneck, and flagging those is the single most valuable thing a VSM does.
Current state, then future state
Practitioners map the current state first — honestly, warts and all — then design a future state that removes the biggest sources of waste. Comparing the two, side by side, is how improvement gets planned and communicated.
Why not sticky notes?
VSMs are traditionally drawn on whiteboards with Post-its, then re-typed into Excel to do the math. That round-trip is slow and error-prone. A calculating canvas like PruneChart keeps the drawing and the arithmetic in one place — Takt, lead time and PCE update as you type, and above-Takt steps flag themselves.