Flow Efficiency Calculator
This flow efficiency calculator shows how much of a process's lead time is spent working on the item and how much is spent waiting. Enter the work time at each step and the wait that follows it, as you would read them off a value stream map.
Each step's work time and the wait before the next step
Flow efficiency
3.9%
- Work time
- 5.5 hours
- Waiting
- 136 hours
- Lead time
- 141.5 hours
Work is moving 3.9% of the time and waiting 96.1%. The longest wait is after Painting (48 hours). Halving it would cut lead time by 17.0%.
On a value stream map this is the timeline ladder: waits on the upper rungs, work on the lower ones. The green slivers are the only time the item is being worked on.
Example values are filled in. Replace them with your own; nothing you type leaves your browser.
Worked example
The example values, step by step
- Step 1 · Work time
0.5 + 1.5 + 2 + 1 + 0.5 hours
= 5.5 hours
- Step 2 · Waiting time
16 + 40 + 24 + 48 + 8 hours
= 136 hours
- Step 3 · Lead time
5.5 + 136 hours
= 141.5 hours
- Step 4 · Flow efficiency
5.5 ÷ 141.5
= 3.9%
Reading the result
In the example, a welded frame spends 5.5 hours being worked on and 136 hours waiting between steps. For about 96% of its lead time, nothing is happening to it.
The longest queue is after painting, at 48 hours. Halving that one wait cuts lead time by 17%, more than making every work step twice as fast would.
| Change | Lead time | Flow efficiency |
|---|---|---|
| As is | 141.5 h | 3.9% |
| Halve the wait after painting | 117.5 h | 4.7% |
| Halve every wait | 73.5 h | 7.5% |
| Halve every work step instead | 138.75 h | 2.0% |
Computed from the calculator's example values. Faster work steps shorten lead time a little but lower the ratio, because waits now take up a larger share.
Common data mistakes
- Counting all work time as value-added. Inspection, rework and internal handoffs are work, but the customer would not pay for them.
- Using planned or standard times instead of timing real items.
- Leaving out the wait before the first step, such as an order sitting in an inbox.
- Mixing units, such as minutes for work and days for waits, without converting.
The methods behind the number
The formula
How it's calculated
- Lead time
- Total work time + Total waiting time
- Flow efficiency
- Value-added (work) time ÷ Lead time × 100
Flow efficiency and resource efficiency
Resource efficiency asks how busy people and machines are. Flow efficiency asks how busy the item is. Keeping every resource busy tends to build queues, and queues lower flow efficiency.
Also called process cycle efficiency
In Lean Six Sigma the same ratio is often called process cycle efficiency (PCE). The formula is the same: value-added time divided by total lead time.
Measure the item, not the plan
Follow real items through the process and time them, or take dates from your workflow tool. Planned or standard times hide the waits you are trying to find.
Frequently asked questions
What is the formula to calculate flow efficiency?
Is flow efficiency the same as process cycle efficiency?
How do you improve flow efficiency?
What is a good flow efficiency?
How is flow efficiency used in kanban for software teams?
Sources and further reading
- Niklas Modig and Pär Åhlström, This Is Lean (book)
- Lean Enterprise Institute lexicon: value-stream mapping ↗
- Mike Rother and John Shook, Learning to See (book) ↗
For vendors
Built a lean tool?
Submit it for review. Every tool is checked against our listing criteria and researched from public sources. Approved tools join their category in the next published batch.