FSN Inventory Analysis: Fast, Slow & Non-Moving Classification, Formula & Example

FSN analysis classifies inventory according to how quickly or frequently it moves: Fast-moving (F), Slow-moving (S) and Non-moving (N). It helps identify which items need frequent replenishment attention and which items may be tying up working capital or warehouse space.

FSN is a movement classification. It is different from ABC, which focuses on annual consumption value, and VED/VEN, which focuses on criticality.

FSN Categories

There Is No Universal FSN Cutoff

A key practical point is that FSN thresholds should be defined by the organisation. A spare part that moves once every six months may be normal in maintenance inventory but would be extremely slow in a supermarket.

Before classifying items, define:

• The analysis period, for example 12 or 24 months.
• What counts as movement: issue, sale, consumption or transfer.
• Whether returns and corrections should be excluded.
• The threshold for Fast, Slow and Non-moving.
• Whether critical spares require separate treatment.

Method 1: Days Since Last Movement

One simple approach is to calculate:

Days since last movement = Analysis date − Last valid issue date

An example policy might be:

• F: movement within the last 30 days.
• S: last movement 31–180 days ago.
• N: no movement for more than 180 days.

These numbers are only an example. The business should set thresholds that fit its products, lead times and industry.

Method 2: Issue Frequency

Another method uses how often an item moved during the analysis period:

Movement frequency = Number of valid issue transactions ÷ Analysis period

For example, over 12 months:

The company might define F as more than 12 issues/year, S as 1–12 and N as zero. Again, the cutoff is a policy choice rather than a universal standard.

Worked Example

Assume a maintenance warehouse reviews 12 months of usage:

The classification does not mean Seal C should automatically be scrapped. If it protects a critical asset with a 12-month replacement lead time, it may be intentionally retained despite being non-moving.

FSN Actions by Category

Fast-moving

• Monitor service level and stockouts.
• Review reorder points frequently.
• Position in accessible warehouse locations.
• Check supplier reliability and lead time.

Slow-moving

• Validate forecast or requirement.
• Review MOQ and order frequency.
• Consider centralising stock.
• Check whether safety stock is excessive.

Non-moving

• Confirm whether the item is still technically required.
• Check open contracts, equipment lists and future projects.
• Redeploy to another location where useful.
• Return to supplier if contractually possible.
• Sell, recycle or dispose under approved controls where appropriate.

Combine FSN with ABC and VED

FSN becomes more powerful when combined with other classifications:

• A-N: high-value item that has stopped moving — strong working-capital review candidate.
• C-F: low-value fast mover — automate replenishment where possible.
• V-N: critical but non-moving spare — may still justify stock because movement is not the same as importance.

This prevents a common mistake: treating all non-moving stock as unnecessary.

Useful KPIs

• Value of non-moving inventory.
• Percentage of inventory value by FSN class.
• Slow/non-moving stock ageing.
• Stockout rate for fast movers.
• Write-off / disposal value.
• Inventory turns.

Common Interview Question

Question: What is FSN analysis?

Strong answer: FSN classifies inventory by movement rate into fast, slow and non-moving items. I would define a suitable analysis period and movement thresholds, then combine the result with value and criticality classifications before changing stocking policy.

Related SCMANA Guides

• ABC vs VED/VEN Analysis
• VED Analysis
• Inventory Holding Cost & EOQ

Download the Practical Workbook

Use the SCMANA FSN Inventory Analysis Workbook to classify items by movement rate and work through fast-, slow- and non-moving inventory logic.

Download the FSN Inventory Analysis Workbook (Excel)