The Stroke Difficulty Score (SDS) measures the true physical cost of executing a stroke accurately under working conditions.
It accounts for four things:
How many keys you’re pressing
How your fingers coordinate
How the stroke degrades when tired
How pressure affects execution
The SDS predicts which strokes stay accurate when fatigue sets in and which strokes challenge consistency late in depositions.
The Formula
SDS = K × (1 + C) × (1 + F) × (1 + S)
Where:
K = Key count (baseline)
C = Coordination complexity (0 to 2.0)
F = Fatigue factor (0 to 1.0)
S = Speed/pressure factor (0 to 0.5)
K = Key Count
Simply the number of keys in the stroke.
3 keys = K of 3
7 keys = K of 7
More keys = more work. That’s the baseline.
C = Coordination Complexity (0 to 2.0)
How difficult is the finger pattern to execute?
What Increases C:
Both hands working together: When you use both hands, you’re coordinating between left and right sides of your brain. That’s overhead cost. (+0.3)
Non-adjacent fingers: Pressing T (left ring top) and H (left index top) - skipping the middle finger - requires your hand to spread unnaturally. (+0.2 per occurrence)
Crack positions: When one finger presses both top AND bottom keys simultaneously (like right index pressing F top and R bottom), that’s a crack position. It requires precise positioning. (+0.3 per crack)
Asterisk complexity: The asterisk adds difficulty in two ways. First, the right index finger must make an unnatural reach to hit it, which adds both coordination difficulty and execution time. Second, the asterisk requires precise timing - not too early, not too late, exactly with the other keys. Both the reach and the timing precision increase coordination complexity. (+0.4)
Pinky stretches: Using both left pinky (S-) AND right pinky (-Z or -D) in the same stroke requires wide lateral movement. (+0.2)
Example: “mischaracterizing”
Magnum Steno: PH*EURBGT (9 keys)
Starting SDS: 9.00 (9 keys)
Coordination penalties:
Both hands: +0.3
PH combination (left middle + left index): +0.2
Asterisk (unnatural reach + timing): +0.4
Crack position (right index * and R): +0.3
Total C = 1.2
Base SDS = 9 × (1 + 1.2) = 9 × 2.2 = 19.8
BREVITY: PH-FG (4 keys)
Starting SDS: 4.00 (4 keys)
Coordination penalties:
Both hands: +0.3
Total C = 0.3
Base SDS = 4 × (1 + 0.3) = 4 × 1.3 = 5.2
F = Fatigue Factor (0 to 1.0)
How much fatigue degrades execution.
Three levels:
Fresh (F = 0):
First hour of work
Well-rested
Sharp focus
No accumulated stress
Normal Working (F = 0.5):
Hours 2-4
Moderate fatigue
Sustainable pace
Typical deposition conditions
Late Day (F = 1.0):
Hours 5+
Significant fatigue
Reduced accuracy
End of long depositions
Why F Matters:
Complex strokes degrade faster under fatigue. A stroke with high coordination complexity (high C) multiplies that complexity by fatigue.
Example: PH*EURBGT at different fatigue levels
Base SDS = 19.8
Fresh: 19.8 × (1 + 0) = 19.8
Normal: 19.8 × (1 + 0.5) = 29.7
Late day: 19.8 × (1 + 1.0) = 39.6
The stroke gets TWICE as difficult when tired.
Meanwhile, PH-FG stays at 5.2 base, reaching only 10.4 when fully fatigued - still easier than the Magnum stroke when fresh.
S = Speed/Pressure Factor (0 to 0.5)
How much time pressure affects execution.
Three levels:
Relaxed (S = 0):
No time pressure
Comfortable pace
Full attention available
Normal Pace (S = 0.25):
Standard professional speed
Manageable pressure
Typical working conditions
High Pressure (S = 0.5):
Fast testimony
Interruptions
Contentious depositions
Multiple speakers
Why S Matters:
Speed pressure reduces execution precision. Complex finger patterns suffer more than simple ones.
Example: PH*EURBGT under pressure
At normal working fatigue (F = 0.5):
Base = 19.8 × 1.5 = 29.7
Relaxed: 29.7 × (1 + 0) = 29.7
Normal pace: 29.7 × (1 + 0.25) = 37.1
High pressure: 29.7 × (1 + 0.5) = 44.6
Complete Calculation Example
Let’s calculate the full working SDS for both versions of “mischaracterizing” under typical conditions (Normal fatigue, Normal pace):
Magnum Steno: PH*EURBGT
Start with keys: 9.00
Apply coordination: 9.00 × (1 + 1.2) = 19.8
Apply fatigue: 19.8 × (1 + 0.5) = 29.7
Apply speed: 29.7 × (1 + 0.25) = 37.1
BREVITY: PH-FG
Start with keys: 4.00
Apply coordination: 4.00 × (1 + 0.3) = 5.2
Apply fatigue: 5.2 × (1 + 0.5) = 7.8
Apply speed: 7.8 × (1 + 0.25) = 9.75
Result: 74% reduction in stroke difficulty
What SDS Tells You
SDS < 10: Easy to execute accurately even when tired
SDS 10-20: Manageable with focus
SDS 20-30: Requires significant effort, accuracy suffers under fatigue
SDS > 30: High error risk, especially late day
Common Questions
Q: “But I can write PH*EURBGT fast and accurately!”
A: That’s great! But ask yourself:
Can you still write it accurately as fatigue builds?
How much mental effort does it require?
Would you rather spend that effort on the testimony?
The formula predicts sustainability, not momentary capability.
Q: “I prefer my brief for ‘mischaracterizing’”
A: You might prefer a certain brief
But if it has SDS > 25, you’ll correct it frequently
Preference doesn’t override biomechanics
Q: “Isn’t this just for one theory?”
A: No. SDS works for ANY stenographic theory:
Traditional theories
Magnum Steno
Phoenix
StenEd
BREVITY
Your custom dictionary
It’s universal. That’s what makes it scientific.
Q: “What if I disagree with the penalties?”
A: The penalties are based on biomechanics and cognitive science:
Both hands requiring coordination = neuroscience fact
Crack positions requiring precision = anatomical fact
Fatigue affecting performance = universal experience
But you can adjust for your personal physiology if needed. The framework remains valid.
How To Calculate SDS For Your Outlines
Method 1: Manual Calculation
Count the keys (K)
Identify all coordination factors (C)
Add them up
Set your fatigue level (F)
Set your speed level (S)
Multiply: K × (1 + C) × (1 + F) × (1 + S)
Method 2: Use The Calculator
The BREVITY Complete Analyzer includes an outline calculator:
Enter any outline
Select fatigue and speed
Instant SDS calculation
Detailed breakdown shown
Works for any theory
The Keyboard Real Estate Problem: Why Stroke Allocation Matters
Understanding SDS isn’t just about measuring individual stroke difficulty. It reveals a fundamental design flaw in brief-heavy systems: the misallocation of keyboard real estate.
The principle should be simple: Words you write constantly should occupy the simplest strokes in the most accessible keyboard positions. Frequency should determine allocation.
Words you write 50 times per page should get the lowest SDS - fewest keys, simplest coordination, prime keyboard positions.
Words you write once every thousand pages should use whatever’s left over.
But Magnum Steno and many other theories do the opposite.
The “Ally” Problem
Magnum Steno assigns AEL (a 3-key, easy, prime left-hand stroke) to the word “ally.”
How often does “ally” appear in legal depositions?
Virtually never. In thousands upon thousands of pages of testimony, “ally” simply doesn’t come up. Unless something literally happened in an alley (the narrow passage between buildings), you’ll never write this word. And even then, that’s not typical of high-litigation cases.
Yet AEL - a low-SDS stroke in prime keyboard real estate - sits waiting for a word that will never appear.
Meanwhile, common words that appear 50+ times per page get assigned complex 7-10 key strokes with high SDS.
The Math of Misallocation
Let’s quantify the waste:
“Ally” with AEL:
Frequency: 0 times per page (essentially never)
SDS: ~3.75 (low - easy execution)
Total physical cost per page: 0 × 3.75 = 0
AEL wasted on a word you never write
Common word with complex stroke:
Frequency: 50 times per page
SDS: 25-40 (high - difficult execution)
Total physical cost per page: 50 × 30 = 1,500
High difficulty multiplied by high frequency = exhausting
The backwards allocation: The easy stroke goes unused. The common words get difficult strokes that you must execute dozens of times per page, compounding physical fatigue.
Why This Happens
Brief-heavy systems weren’t designed with frequency analysis. They were designed with:
Phonetic logic (”AEL sounds like ‘ally’”)
Dictionary completeness (must have a brief for every word)
Theoretical coverage (even if you’ll never use it)
But frequency wasn’t the primary design criterion.
Result: Keyboard real estate allocated by phonetics and theory, not by actual usage patterns in legal testimony.
The BREVITY Approach
BREVITY does the opposite - common words get the easiest strokes:
Skeletal Writing means:
High-frequency words naturally become short
Remove vowels = fewer keys = lower SDS
Most common words reduce to 2-4 keys
Frequency-based optimization:
Don’t memorize briefs for rare words
Save memory and keyboard space for what you actually write
Let common words have the prime real estate
The math:
Common word (50x per page) with low SDS (6) = 50 × 6 = 300 physical cost
Rare word? Write it out when/if it appears
Physical cost concentrated where it matters, minimized where it doesn’t
This Is System Design
The SDS formula doesn’t just measure individual strokes. It exposes systemic design flaws:
Poor design: Easy strokes wasted on rare words, difficult strokes assigned to common words.
Optimal design: Common words get lowest SDS, keyboard real estate allocated by frequency.
When you can measure physical cost objectively (SDS), you can see that brief systems allocate keyboard resources backwards - giving easy strokes to words you never write while forcing you to execute difficult strokes dozens of times per page.
This isn’t just inefficient. It’s exhausting by design.
The Bottom Line
SDS measures what matters: physical execution cost.
Low SDS = sustainable careers High SDS = burnout and dropouts
For the first time in stenography history, you can measure difficulty objectively.
Use it to:
Evaluate outlines before learning them
Understand why you struggle with certain briefs
Make evidence-based career decisions
Choose sustainability over theoretical efficiency
Your career depends on it.
Coming Up
DLS (Decision Load Score) - Measuring mental burden and memory cost
The Cohen Brothers & Dom Tursi - Analyzing competing philosophies with the formulas
CEF (Context Effect Factor) - How corrections cascade and compound
The Mathematics of Mastery - Building sustainable stenographic excellence
Tom Fernicola 36 years professional court reporting Creator, BREVITY Stenography System Author, “BREVITY: Write Simply”
SDS is part of the first objective measurement framework in 140+ years of stenography history. All calculations in this article are reproducible and verifiable.