Film Roll Yield and Roll Change Calculator
Enter your film roll, bag repeat length and machine settings to see how many bags one roll makes, how often you change rolls, and how many rolls you need per day or per order. By YLTPACK, flexible packaging manufacturer.
Default values are examples. Each default is a typical value, please confirm with your data.
Film roll
Bag and machine
Production schedule
Order
Per roll
Length worked out from roll weight, width, thickness and density.
Whole bags one roll can make at your bag repeat length.
Minutes of running before the roll is used up, at effective speed.
Run time plus roll change time: one full roll cycle.
Machine output
Average rolls used in one shift, including roll change time.
Estimated output of one shift at your efficiency.
Bags per shift multiplied by shifts per day.
Rolls used per day across all shifts.
Bags per day multiplied by working days per month.
Your order
Film needed for the order, including the waste allowance.
Total film length divided by roll length, rounded up. Treat the order quantity as monthly demand to get rolls per month.
Estimated film weight for the order, from width, thickness and density.
Working days to make the order quantity at this daily output.
How it's calculated
Formulas
- Film weight per m² (g/m²) = thickness (µm) × density (g/cm³).
- Roll length (m) = roll weight (kg) × 1000 ÷ (web width (m) × g/m²), where web width (m) = web width (mm) ÷ 1000. Used only when 'I only know roll weight' is ticked.
- Bags per roll = floor(roll length (m) × 1000 ÷ bag repeat length (mm)).
- Run time per roll (min) = bags per roll ÷ (machine speed × efficiency).
- Cycle per roll (min) = run time per roll + roll change time.
- Rolls per shift = shift minutes (hours × 60) ÷ cycle per roll. Bags per shift = rolls per shift × bags per roll. Daily values = per-shift values × shifts per day.
- Total film length (m) = order quantity × bag repeat length (mm) ÷ 1000 × (1 + waste allowance). Rolls required = ceil(total film length ÷ roll length).
- Film weight (kg) = total film length (m) × web width (m) × g/m² ÷ 1000.
- Imperial conversions: 1 ft = 0.3048 m, 1 in = 25.4 mm, 1 mil = 25.4 µm, 1 lb = 0.45359237 kg. Density stays in g/cm³.
Default assumptions
- Every default value is a typical value, please confirm with your data.
- Bag repeat length is the film length used per bag (cut to cut), including seal areas.
- Efficiency is applied to machine speed and is meant to cover stoppages, roll changes and adjustments. If your efficiency figure already counts roll changes, set roll change time to 0 to avoid counting them twice.
- Order quantity is the quantity for the period you plan (for example one month). Core waste, splices and start-up scrap beyond the waste allowance are not included.
- The default density of 1.0 g/cm³ is a typical value, please confirm with your data. Real film structures differ.
How to use
Enter your film roll
Type the roll length, or tick the box and enter roll weight, web width, thickness and density.
Set bag and machine
Enter the bag repeat length, machine speed, efficiency and the time you need to change a roll.
Read your results
Add your shift pattern and order quantity. Results update instantly, and you can switch between Metric and Imperial at any time.
A worked example
These steps use the default values: 1,000 m roll, 200 mm bag repeat, 60 bags/min at 85% efficiency, 5 min roll change, 8 h × 1 shift, 22 days, 500,000 bags, 3% waste, 300 mm web width, 50 µm, 1.0 g/cm³.
| Item | Calculation | Result |
|---|---|---|
| Bags per roll | floor(1,000 m × 1000 ÷ 200 mm) | 5,000 bags |
| Run time per roll | 5,000 ÷ (60 × 0.85) | 98.0 min |
| Cycle incl. roll change | 98.04 + 5 min | 103.0 min |
| Rolls per shift | 480 min ÷ 103.04 min | 4.66 rolls |
| Bags per shift | 4.658 × 5,000 | 23,292 bags |
| Bags per day | 23,292 × 1 shift | 23,292 bags |
| Monthly capacity | 23,292 × 22 days | 512,426 bags |
| Total film length | 500,000 × 200 ÷ 1000 × 1.03 | 103,000 m |
| Rolls required | ceil(103,000 ÷ 1,000) | 103 rolls |
| Film weight needed | 103,000 m × 0.3 m × 50 g/m² ÷ 1000 | 1,545 kg |
| Production days needed | 500,000 ÷ 23,292 | 21.5 days |
The calculator keeps unrounded values between steps, so a hand calculation with rounded figures can differ slightly.
FAQ
How do I find the roll length if I only know the roll weight?
Tick 'I only know roll weight' and enter the net film weight, web width, thickness and density. The calculator converts these to length with: length = weight × 1000 ÷ (width in m × thickness × density).
What should I enter as the bag repeat length?
Use the length of film your machine pulls for one bag, measured cut to cut. It normally includes the seal areas. If the film is printed, it should match the print repeat on the film.
Why are efficiency and roll change time separate inputs?
Efficiency reduces the effective bag speed for stoppages and adjustments. Roll change time is added on top as a fixed stop for each roll. If your efficiency figure already includes roll changes, set roll change time to 0.
How much waste allowance should I use?
It depends on your machine, set-up routine and print registration. The 3% default is a typical value, please confirm with your data. Use your own scrap records if you have them.
Can the roll size be adjusted to suit my machine?
Roll width, core size and outside diameter depend on your packaging machine and the project. Share your machine limits and bag size with us, and we will confirm the roll specification in your quotation.
Related tools
Film Weight Calculator
Estimate roll or order weight from width, thickness and density.
Pouch Size and Film Width Calculator
Work out the web width needed for your bag or pouch size.
Packaging Cost per Bag Estimator
Plan the film cost per bag from your film and order details.
Roll Outside Diameter Calculator
Check that a roll fits your unwind holder.
Have a project in mind?
Tell us your bag size, film structure and machine, and the YLTPACK team will prepare a quotation for your roll film.
Get a Free QuoteResults are estimates for planning purposes. Final specifications and prices are confirmed in your quotation.