What does FS/PSD stand for?

FS stands for Fibromyalgia Symptom scale and PSD stands for Polysymptomatic Distress scale. They are two names for the same combined score — WPI plus SSS — on a 0 to 31 scale. Some clinicians and papers use FS, others use PSD; the calculation is the same.

What is a normal FS/PSD score?

There is no single normal score for everyone. WPI ranges from 0 to 19 and SSS from 0 to 12, so the combined total can reach 31. Lower scores generally mean milder symptom burden, but interpretation depends on your history, treatment and what your clinician is looking for. These scores support monitoring — they are not a reason to change treatment on your own.

How often should FS/PSD be measured?

In clinic, WPI and SSS are often completed at appointments or during assessment. For personal tracking, logging widespread pain, fatigue, sleep and cognitive symptoms regularly gives a clearer picture than trying to recall how the past weeks felt from memory.

Can I calculate FS/PSD myself?

You can if you know your WPI (painful body regions in the past week) and your SSS components — fatigue, waking unrefreshed, cognitive symptoms and somatic symptoms, each rated 0 to 3. Add WPI and SSS for the combined total. Many people rely on their clinician for the official clinical assessment.

Does Hurtl calculate FS/PSD automatically?

Yes. Hurtl calculates an FS/PSD estimate from your daily logs — widespread pain and symptom severity — with a 7-day trend on the Condition tab. Log once a day and your score updates automatically; no need to run the calculator manually each time.

Is there a free FS/PSD calculator?

Yes. This article includes a free FS/PSD calculator. For a score that updates daily from your symptom logs, use the Hurtl fibromyalgia tracker on iPhone.

25 June 2026

What Is FS/PSD and How Is It Calculated?

By Tom, founder of Hurtl.

If you live with fibromyalgia, you may hear your clinician mention FS or PSD — or see them written together as FS/PSD. Both refer to the same combined score built from the Widespread Pain Index (WPI) and Symptom Severity Scale (SSS): a structured way to capture how widespread your pain is and how severe fatigue, sleep disruption and cognitive symptoms have been.

What is FS/PSD?

FS stands for Fibromyalgia Symptom scale. PSD stands for Polysymptomatic Distress scale. They are two names for the same total — the sum of WPI and SSS on a 0 to 31 scale. Research papers and clinics use either term; the calculation is identical.

That combined score is built from two patient-reported measures used in modern fibromyalgia assessment:

WPI — the Widespread Pain Index (0 to 19)
SSS — the Symptom Severity Scale (0 to 12)

Together, WPI and SSS reflect the two pillars clinicians look at in fibromyalgia: pain spread across the body and severity of core non-pain symptoms like fatigue and unrefreshed sleep. FS/PSD rolls both into one number your care team can track over time.

Clinicians use WPI and SSS because they are:

Patient-reported — you describe your experience rather than relying on blood tests or imaging
Standardised — the same body regions and symptom questions are used visit to visit
Repeatable — scores can be compared over months to see whether symptoms are improving or worsening

FS/PSD is not a diagnosis tool on its own. Fibromyalgia assessment also depends on how long symptoms have been present, whether other conditions could explain them, and your clinician’s full evaluation. The scores support monitoring and treatment discussions — they do not replace clinical judgement.

The two components of FS/PSD

1. Widespread Pain Index (WPI) — 0 to 19

The WPI counts how many of 19 defined body regions have been painful in the past week. Each region counts once — left and right sides are scored separately.

Typical regions include:

Jaw, neck, upper and lower back, chest, abdomen
Shoulder, upper arm, lower arm, hip/buttock, upper leg and lower leg — each side counted separately

Higher WPI = pain in more body areas. A score of 0 means no painful regions were reported; 19 means pain was present in every region.

Fibromyalgia is associated with widespread pain, but the WPI alone does not diagnose the condition. Your clinician interprets it alongside symptom severity and your overall history.

2. Symptom Severity Scale (SSS) — 0 to 12

The SSS rates how severe three core symptoms have been over the past week, each on a 0 to 3 scale (0 = no problem, 3 = severe):

Fatigue
Waking unrefreshed — non-restorative sleep
Cognitive symptoms — problems with thinking, concentration or memory (sometimes called “fibro fog”)

A fourth part covers somatic symptoms — headache, pain or cramps in the lower abdomen, and depression. In clinic, each is usually scored for presence (0 or 1) over the past six months, and the combined contribution is capped at 3 for the total SSS.

SSS maximum = 12 (3 + 3 + 3 + 3).

How FS/PSD is calculated

In clinic, your clinician adds WPI and SSS to get the FS/PSD total:

FS/PSD (Fibromyalgia Symptom / Polysymptomatic Distress) = WPI + SSS

The combined total can range from 0 to 31.

These scores are also used in 2016 ACR fibromyalgia criteria — research thresholds that clinicians may reference during assessment. As a rough guide (not for self-diagnosis):

WPI ≥ 7 and SSS ≥ 5, or
WPI 4–6 and SSS ≥ 9

…alongside other clinical requirements such as symptoms at a similar level for at least three months and no other disorder that fully explains them.

Your clinician applies the full criteria in context. Do not use these thresholds to diagnose or rule out fibromyalgia yourself.

Worked example

Component	Detail	Score
WPI	Pain in 8 body regions this week	8
Fatigue	Moderate	2
Waking unrefreshed	Severe	3
Cognitive symptoms	Moderate	2
Somatic symptoms	Headache + depression (combined)	2
SSS subtotal	2 + 3 + 2 + 2	9

FS/PSD total: 8 + 9 = 17

Try the calculator

Use the tool below with your own numbers — tick painful body regions, rate your core symptoms and note any somatic symptoms. WPI and SSS update as you go.

What do FS/PSD scores mean?

Unlike inflammatory arthritis scores with widely cited remission cutoffs, fibromyalgia scoring is used more for assessment and monitoring than fixed treatment targets. There is no universal “good” score for everyone.

As a general guide:

Lower WPI and SSS usually mean milder widespread pain and fewer severe core symptoms
Higher totals suggest more widespread pain and/or more severe fatigue, sleep disruption and cognitive symptoms
Trend over time matters more than a single number — is your total falling after starting a new treatment or therapy, or creeping up before a flare becomes obvious?

These cutoffs are not rules you should apply on your own to change treatment. Always discuss results with your care team.

Why memory makes clinic scores hard

WPI and SSS ask about the past week, but many people answer from how they feel today. You might be in a flare this morning and forget that pain was manageable most of last week — or the opposite. That recency bias can make clinic scores less accurate than your real experience.

Fibromyalgia symptoms also shift in ways that are hard to summarise in one sitting. You might remember widespread pain clearly but under-report brain fog, or forget how many mornings you woke unrefreshed. A modest daily log creates a reference point instead of guesswork.

How tracking supports FS/PSD in practice

You do not need to calculate FS/PSD manually every day. Log the underlying symptoms your clinician will ask about — Hurtl turns them into a running FS/PSD estimate:

Widespread pain and where it shows up
Fatigue
Sleep quality and whether you woke unrefreshed
Cognitive symptoms (“fibro fog”)
Flares and what may have triggered them
Medication and treatment adherence

Hurtl calculates an FS/PSD estimate daily from your logs on the Condition tab, with a 7-day trend. It is an estimate from your entries, not an official clinical score. You can also export a clinical PDF report with symptom trends, period comparison and medication adherence so appointments start from what you recorded, not memory.

See our fibromyalgia symptom tracker to get started, or read why track symptoms between appointments for habits that make any score more meaningful.

This article explains FS/PSD for general information only. It is not medical advice, a diagnosis, or a recommendation to start, stop, or change treatment. FS/PSD scores should be interpreted by your clinician in the context of your full clinical picture. Hurtl is not a medical device and does not provide clinical monitoring or treatment decisions.