Yield tells you where your process is quietly losing the project.
First Time Yield and Rolled Throughput Yield are the two quality metrics that separate "it eventually shipped" from "it worked the first time." This micro-course covers the definitions, formulas, calculations, and how to use each metric on a real project.
First Time Yield
The foundation metric: how much of what you started came out right, the first time, with no rework, no scrap, and no fixes.
What Is First Time Yield (FTY)?
First Time Yield measures the percentage of units, deliverables, or tasks that complete a process step correctly on the first attempt — with no defects, no rework, and no scrap. It's the cleanest possible read on how a single step is performing, because it strips out any credit for units that only passed after being fixed.
Because it's scoped to one step, FTY is the metric a task owner or station lead can act on directly — it points at their process, not the whole value stream.
Why Monitor FTY?
FTY is a leading indicator. Cost and schedule overruns are lagging indicators — by the time they show up in a status report, the damage is already done. FTY surfaces the same problem while it's still cheap to fix: at the station where the defect was actually introduced.
- Early warning: a dip in FTY at one step flags process drift before it reaches the customer or the next station.
- Cost control: rework and scrap are direct, avoidable cost — FTY quantifies exactly how much of it exists.
- Accountability with data: replaces "it feels like Assembly is slower lately" with a tracked, comparable percentage.
- Baseline for improvement: you can't prove a fix worked without a before-and-after FTY number.
Importance of FTY in Six Sigma
FTY is one of the core metrics of the Six Sigma toolkit because it feeds directly into the math that defines process capability. In the Measure phase of DMAIC, FTY is typically the first quality baseline established for a process before any improvement work begins.
FTY connects to the other core Six Sigma quality metrics:
- DPU (Defects Per Unit) — the average count of defects per unit produced.
- DPMO (Defects Per Million Opportunities) — DPU normalized to a common scale for benchmarking.
- Sigma Level — the process capability rating (a "Six Sigma" process runs at 99.99966% yield, or 3.4 DPMO).
FTY is measured before inspection and rework mask the true defect rate. Six Sigma is built on eliminating variation at the source — FTY is the metric that shows where the source actually is.
How Monitoring FTY Regularly Facilitates Improvement
Tracking FTY as an ongoing cadence — not a one-time audit — changes what a team can do with the data. Regular monitoring facilitates:
Catching defects and process drift close to the moment they're introduced, instead of downstream.
Quantifying the Cost of Poor Quality (COPQ) tied to rework, scrap, and repair labor.
Ranking which step, station, or team needs improvement attention first, based on data rather than opinion.
Distinguishing a one-off blip from a sustained decline that signals a real process problem.
Giving station owners a clear, comparable number they can own and improve.
Comparing performance across shifts, lines, teams, or vendors on equal footing.
Reducing the odds that a defect reaches the customer or the next internal step undetected.
Supplying the before/after evidence that a Kaizen event or improvement project actually worked.
Rolled Throughput Yield
FTY tells you about one step. RTY tells you about the whole process — and it's almost always lower than you'd guess.
What Is Rolled Throughput Yield (RTY)?
Rolled Throughput Yield is the probability that a single unit passes through every step of a multi-step process with zero defects at any point along the way. It's calculated by multiplying — "rolling up" — the FTY of every individual step, not by averaging them.
That multiplication is what makes RTY powerful: a handful of steps that each look "fine" on their own can compound into a process that fails far more often than any one step suggests.
Why Does Rolled Throughput Yield Matter?
Explanation: RTY exposes what's often called the "hidden factory" — the true rate of rework and scrap that gets masked once inspection and repair loops clean things up before the final count. A process can report a high final pass rate purely because of downstream fixing, while the RTY behind it is much lower.
Purpose: RTY gives leadership an honest, end-to-end capability number for the whole process — the metric to use when deciding whether the process itself needs redesign, not just a patch at one station.
Why Are FTY and RTY Important to a Project?
On a project — not just a production line — these metrics translate directly into the three things a project manager is measured on:
| Project Constraint | How FTY / RTY Impacts It |
|---|---|
| Schedule | Rework consumes the schedule buffer that was meant to absorb genuine risk, not repeat work. |
| Cost | Every unit reworked or scrapped is cost paid twice — once to build it, once to fix or replace it. |
| Quality / Scope | Low RTY signals that the delivered scope is at risk of carrying undetected defects into the next phase. |
| Risk | A declining FTY trend is an early-warning risk signal, well before it becomes a missed milestone. |
| Team Morale | Chronic rework creates firefighting culture; visible yield metrics redirect energy toward root cause fixes. |
Applying the Metrics
Knowing the formulas isn't enough — knowing which metric to reach for, and how to move it, is what makes this useful on a live project.
When to Use FTY vs. RTY
| Situation | Use | Why |
|---|---|---|
| Diagnosing one station or task | FTY | Isolates performance to the exact point in the process where you can act. |
| Reporting overall process health | RTY | Reflects true end-to-end capability, including compounding effects. |
| Comparing shifts, teams, or vendors | FTY | Apples-to-apples comparison at the same step across sources. |
| Deciding whether to redesign a process | RTY | Shows whether the problem is one step or the process architecture itself. |
| Root-causing a specific defect type | FTY | Points directly at the step introducing that defect. |
| Setting a project-level quality target | RTY | Represents what the customer or next phase actually experiences. |
Rule of thumb: use FTY to find and fix; use RTY to report and prioritize.
How to Improve First Time Yield
- Root-cause the defects — use tools like the 5 Whys or a fishbone (Ishikawa) diagram before changing anything.
- Error-proof the step (poka-yoke) — design the task so the mistake becomes physically or procedurally difficult to make.
- Standardize the work — write and enforce a single correct procedure instead of letting method vary by person.
- Train and certify — confirm operators or team members can demonstrate the standard, not just read it.
- Control inputs — verify incoming materials, data, or handoffs meet spec before the step even starts.
- Use statistical process control (SPC) — control charts catch drift before it turns into a defect batch.
- Maintain equipment and tools — preventive maintenance removes a common, invisible source of variation.
- Close the loop — re-measure FTY after each change to confirm the fix actually held.
Calculating the Metrics
Worked examples using a simple four-step process, so the formulas turn into numbers you can reuse on your own data.
How to Calculate Throughput Yield in Individual Steps
For each step: take the units that entered, subtract anything that needed rework or was scrapped, and divide the remainder by the units that entered.
Passed First Time = 500 − 35 − 15 = 450
FTY = 450 ÷ 500 = 90%
Repeat this once per step. Below is the FTY for each of the four steps in this example process:
Step-by-Step Guide to Calculating Rolled Throughput Yield
- Map the process — list every step a unit passes through, in order.
- Calculate FTY for each step — using the individual-step formula above.
- Convert each FTY to a decimal — 98% → 0.98, 94% → 0.94, and so on.
- Multiply every step's decimal together — not averaged, multiplied in sequence.
- Convert the result back to a percentage — that's your RTY.
RTY = 0.7107 = 71.1% Even though every individual step looks "acceptable" at 90%+, only about 71 out of every 100 units make it through all four steps defect-free.
Tips on How to Interpret RTY Results
- Don't blame one step. A low RTY is a property of the whole chain — find the lowest individual FTY first; that step usually offers the biggest single improvement.
- Track the trend, not the snapshot. A single RTY reading tells you where you are; a run of readings tells you whether you're improving.
- RTY excludes rework loops on purpose. Don't confuse it with your final pass rate after inspection and repair — RTY is deliberately stricter, because that's where the real cost lives.
- Benchmark against your own baseline first. Six Sigma targets (99.99966%) are aspirational for most processes — a realistic near-term goal is steady improvement over your own historical RTY.
- Use it to prioritize, not to punish. The goal of tracking RTY is to route improvement resources to the highest-leverage step, not to assign blame.
Video Lecture
A companion walkthrough of First Time Yield and Rolled Throughput Yield.