Free industry tools

Winding &
Converting
Calculators

Professional free calculators for the winding and converting industry. Roll geometry, web speed, throughput, tension and more — built for engineers and operators.

UNWIND GUIDE NIPS REWIND WEB PATH 300 m/min FITZGROUP.CO.UK WINDING SCHEMATIC v1.0
100+
Free calculators
4
Categories
Calculator categories
Select a category to open all tools
⊙
Physical Dimensions
Roll diameter, length, caliper, weight, number of turns, slit geometry and reel build calculations.
26 calculators
▶
Running Speed
Surface speed, RPM, winder profiles, draw, accumulator sizing, splice and dancer calculations.
24 calculators
⊟
Throughput
Area/weight output, OEE, waste & yield, rolls per shift, capacity planning and efficiency tools.
25 calculators
⚙
Engineering
Tension, torque, nip load, inertia, taper tension, power, hardness and structural calculations.
27 calculators
About Fitz Group
Industry expertise, free for everyone

Fitz Group provides specialist knowledge and solutions to the winding and converting industry. These calculators represent the day-to-day maths that engineers, operators and managers use on the shop floor — now available free to the whole industry.

All formulas are derived from established industry standards and engineering principles. Results should be verified by a qualified engineer for safety-critical applications.

  • Winding process optimisation
  • Converting line consultancy
  • Tension system engineering
  • Training and knowledge transfer
TENSION PROFILE ROLL DIAMETER → TENSION T₀ T_end
Physical Dimension Calculations
Roll Geometry & Reel Dimensions
Calculate roll diameter, length, caliper, weight, turns, slitting geometry and core dimensions.
Roll Diameter & Length
ROLL DIAMETER FROM LENGTH D = ? d (core) D = √(4Lt/π + d²)
Roll Diameter from Length & Caliper
Core OD
mm
Length
m
Caliper
mm
Roll outer diameter
D = √(4 × L × 1000 × t / π + d²)
ROLL LENGTH FROM DIAMETER L = ? D L = π(D²−d²) / 4t × 0.001
Roll Length from Diameter & Caliper
Core OD
mm
Roll OD
mm
Caliper
mm
Roll length
L = π(D²−d²) / (4t × 1000) metres
CALIPER FROM DIAMETER & LENGTH t = ? x-section t = π(D²−d²) / (4L × 1000)
Caliper from Diameter & Length
Core OD
mm
Roll OD
mm
Length
m
Material caliper
NUMBER OF TURNS TURNS N N = (D − d) / (2t)
Number of Turns on a Roll
Core OD
mm
Roll OD
mm
Caliper
mm
Number of turns
N = (D − d) / (2t)
ROLL WEIGHT W web width W = π(D²−d²)×w×ρ / 4×10⁶
Roll Weight (Wound Reel)
Core OD
mm
Roll OD
mm
Web width
mm
Density
g/cm³
Roll weight
ROLL BUILD-UP RATE Length wound (m) Diam dD/dL = t/(π × D/2) × 2000
Roll Diameter Build-up Rate
Caliper
mm
Current OD
mm
mm diameter per metre wound
mm diameter per 100m wound
Slitting & Converting Geometry
SLITTING LAYOUT master width
Slit Width & Number of Lanes
Master width
mm
Trim per side
mm
Slit width
mm
Lane gap
mm
Number of lanes
Usable width
Width yield
Trim waste
CORE DIMENSIONS wall OD ID ID = OD − 2×t_wall
Core ID from OD & Wall Thickness
Core OD
mm
Wall thickness
mm
Core ID
Mean diameter
REEL WEIGHT FROM GSM GSM W = L × w(m) × gsm / 1000
Reel Weight from Length & GSM
Length
m
Web width
mm
Basis weight
g/m²
Reel weight
BASIS WEIGHT (GSM) CALCULATOR W × 10⁶ L × w(mm) g/m²
Basis Weight (GSM) from Roll Specs
Roll weight
kg
Length
m
Web width
mm
Basis weight
Web & Reel Geometry
Linear Metres per Kilogram
Basis weight
g/m²
Web width
mm
Metres per kg
kg per 100m
m/kg = 10⁶ / (GSM × width_mm)
Diameter at Intermediate Length
Core OD
mm
Caliper
mm
Length wound
m
Current roll OD
D = √(4Lt/π + d²)
Remaining Length on a Partial Roll
Core OD
mm
Current OD
mm
Caliper
mm
Remaining length
Reel Width Yield from Parent Roll
Parent width
mm
Total trim
mm
Reel width
mm
Num reels
×
Yield %
Actual used
Waste
Running Speed Calculations
Web Speed, RPM & Machine Dynamics
Surface speed, RPM conversions, winder profiles, dancer sizing, draw and production timing.
Speed & RPM Conversions
SURFACE SPEED FROM RPM v = ? N rpm v = π × D × N / 60000 m/s
Surface Speed from Roll Diameter & RPM
Diameter
mm
RPM
rpm
Surface speed (m/s)
Surface speed (m/min)
Surface speed (km/hr)
RPM FROM SURFACE SPEED v m/s N = ? N = 60000 × v / (π × D)
Required RPM from Surface Speed
Diameter
mm
Web speed
m/s
Shaft speed (rpm)
Angular velocity (rad/s)
WINDER RPM PROFILE N_start N_end Roll OD → RPM
Winder RPM Profile (Core to Full OD)
Core OD
mm
Max roll OD
mm
Line speed
m/min
RPM at core (max)
RPM at full OD (min)
Speed ratio
SPEED DIFFERENTIAL / DRAW V₁ draw % V₂ > V₁
Speed Differential & Web Draw
Upstream spd
m/min
Downstream spd
m/min
Draw (%)
Speed delta (m/min)
Draw% = (V₂−V₁)/V₁ × 100
Splice Accumulator Storage Required
Line speed
m/min
Splice time
sec
Passes (n)
×
Total storage needed
Dancer travel (each)
Production Time for a Given Length
Roll length
m
Line speed
m/min
Efficiency
%
Net run time
Elapsed (with eff.)
Speed Unit Converter
Speed value
From unit
m/min
m/s
ft/min
km/hr
Gear Ratio & Output Speed
Input speed
rpm
Drive teeth
T
Driven teeth
T
Gear ratio
Output speed
Throughput Calculations
Output, Efficiency & Yield
Area and weight output rates, OEE, waste, yield, rolls per shift, and capacity planning.
Output & Capacity
AREA OUTPUT PER HOUR Speed increase → m²/hr
Area Output per Hour
Line speed
m/min
Web width
mm
Efficiency
%
Gross (m²/hr)
Net (m²/hr)
Net per shift 8h (m²)
Weight Output per Hour
Line speed
m/min
Web width
mm
Basis weight
g/m²
Efficiency
%
kg/hr (net)
t/day (24hr net)
OEE — OVERALL EQUIPMENT EFFECTIVENESS OEE A × P × Q
OEE — Overall Equipment Effectiveness
Availability
%
Performance
%
Quality
%
OEE Score
Rolls per Shift
Shift length
min
Roll length
m
Line speed
m/min
Changeover
min
Rolls per shift
Minutes per roll
Waste & Yield from Trim & Splices
Feed width
mm
Product width
mm
Splice waste
m/roll
Roll length
m
Width yield
Length yield
Overall yield
Machine Utilisation & Downtime
Planned hours
hr
Running hours
hr
Planned stops
hr
Availability (%)
Unplanned downtime
Engineering Calculations
Tension, Torque, Nip & Power
Web tension, torque, nip load, drive power, inertia, taper tension and structural calculations.
Tension & Force
WEB TENSION T (N) web width (mm)
Web Tension — Force & Specific Tension
Web width
mm
Tensile strength
N/15mm
% of T_max
%
Max tension (N)
Set tension (N)
Specific tension (N/m)
TORQUE FROM TENSION F (N) r T = F × r = F × D/2000 Nm
Torque from Web Tension & Roll Radius
Tension
N
Roll diameter
mm
Torque (Nm)
Torque (kgf·m)
Drive Power Requirement
Tension
N
Line speed
m/min
Drive eff.
%
Power at web (kW)
Motor power req. (kW)
P = F × v / (60 × 1000) kW
NIP LOAD F = A_bore × P_bar × 0.1 × N_cyl
Nip Load — PLI & Force from Cylinder
Cylinder bore
mm
Air pressure
bar
Cylinders
×
Roll face width
mm
Nip force (N)
Nip force (kgf)
PLI (N/mm)
Taper Tension Profile
Core OD
mm
Max roll OD
mm
Core tension
N
Taper %
%
Tension at core (N)
Tension at mid OD (N)
Tension at full OD (N)
T(D) = T₀ × [1 − taper% × (D−d)/(D_max−d)]
Rotational Inertia of a Wound Roll
Roll OD
mm
Core/bore ID
mm
Roll width
mm
Density
g/cm³
Mass (kg)
Inertia J (kg·m²)
J = m(R²+r²)/2
About Fitz Group
Winding & Converting
Industry Specialists

Fitz Group delivers expert consultancy, engineering and knowledge to the winding and converting industry. These tools represent our commitment to raising the standard of technical knowledge across the sector.

Who we are

Fitz Group is a specialist consultancy operating in the winding and converting industry. We work with manufacturers, converters, OEMs and operators to optimise processes, solve engineering challenges, and deliver measurable improvements in throughput, quality and efficiency.

Our calculator suite is provided free to the industry as an educational and operational resource. Every formula is derived from established industry practice and validated engineering principles.

What we do

From tension system audits and winding process optimisation to operator training and new line commissioning support — Fitz Group brings deep, hands-on expertise to every engagement.

Website
fitzgroup.co.uk
Location
United Kingdom
Sector
Winding & Converting
Tools
100+ free calculators
Disclaimer

All calculators and results on this site are provided for indicative and educational purposes only. Results must be verified by a qualified engineer before application in safety-critical or commercial settings. Fitz Group accepts no liability for decisions made based on these tools.

Traffic & SEO Guide
How to grow fitzgroup.co.uk

A practical, prioritised roadmap for building organic search traffic to a niche B2B calculator site in the winding and converting industry.

Priority actions (do these first)
01
Target long-tail search queries

Engineers search for very specific things. Target exact-match queries like "roll diameter calculator mm" or "web tension calculator converting". Each calculator page should have a unique title tag and H1 matching these terms.

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02
Submit to Google Search Console

As soon as your site is live on fitzgroup.co.uk, verify ownership in Google Search Console and submit your sitemap.xml. This is free and tells Google your site exists. Do it on day one.

Tip: Generate a sitemap with one URL per page (home, dimensions, speed, throughput, engineering, about). Submit at search.google.com/search-console.
03
Add structured data (Schema.org)

Add JSON-LD schema markup for each calculator as a "WebApplication" or "SoftwareApplication" schema. This helps Google understand what each tool does and can trigger rich results in search.

Quick win: Add Organization schema to your homepage with name "Fitz Group", url "fitzgroup.co.uk", and description of what you do.
04
Write supporting articles

Each calculator topic is a blog post opportunity. "How to calculate roll diameter" — 600 words, include the formula, worked example, and link to the calculator. This captures informational search intent and funnels to the tool.

how to calculate roll diameter what is web tension OEE explained manufacturing taper tension winding
05
Build links from industry sites

Reach out to industry associations (PITA, TAPPI, EFIA), converting magazines (Labels & Labeling, Packaging News), and LinkedIn groups. A single link from a respected trade site is worth dozens of generic ones.

Strategy: Post a "free tool" announcement in relevant LinkedIn groups and subreddits like r/manufacturing. Engineers share useful tools.
06
Optimise page speed & Core Web Vitals

This single-file site loads fast by default. Ensure your hosting is UK-based or CDN-backed (Cloudflare free tier is excellent). Target LCP < 2.5s. Google uses speed as a ranking signal.

Test at: pagespeed.web.dev — aim for 90+ on mobile and desktop.
Ongoing content strategy

The most powerful long-term strategy is becoming the definitive reference for winding and converting knowledge online. Here's a 12-month content plan:

Months 1–3: Foundation

Get indexed. Verify Search Console, submit sitemap, ensure all calculator pages have unique meta titles/descriptions. Write 4–6 explainer articles. Share on LinkedIn.

Months 4–6: Content volume

Publish 2 articles per month. Focus on "what is X" and "how to calculate X" queries. Interlink all articles to relevant calculators. Build an email newsletter for industry subscribers.

Months 7–12: Authority

Guest posts on trade publications. Build a glossary of 100+ winding/converting terms. Add a "material density" and "unit conversion" reference library. These become link magnets.

Target keywords by category
Dimensions
roll diameter calculatorroll length calculator caliper calculator filmnumber of turns calculator reel weight calculatorgsm calculator slitting width calculator
Speed
surface speed calculatorrpm to m/min calculator winder rpm calculatorweb draw calculator dancer accumulator sizing
Throughput
OEE calculatorconverting yield calculator rolls per shift calculatormachine utilisation calculator trim waste calculator
Engineering
web tension calculatortorque calculator winding nip load calculatortaper tension calculator drive power calculatorinertia calculator roll