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Greenhouse Plastic Calculator

Calculate the exact plastic size and thickness for your greenhouse with our easy Greenhouse Plastic Calculator. Fast, accurate, and beginner-friendly tool.

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Recommended: 2-4 ft for imperial, 0.6-1.2 m for metric

Building a greenhouse is exciting, but choosing the right plastic size and thickness can be confusing. If you use too little, you’ll fall short. If you use too much, it becomes wasteful and costly. That's why we developed this Greenhouse Plastic Calculator — to help growers like you easily calculate how much greenhouse plastic you need, without guessing or measuring wrong.

Whether you’re growing vegetables, flowers, or starting seeds, using the correct size and type of plastic can make your greenhouse more efficient and longer-lasting.

How to Calculate Plastic for a Greenhouse

To calculate the plastic needed, you need to know four basic dimensions of your greenhouse:

  • Length (A)
  • Height (B)
  • Arch span or width (C)
  • End wall width (D)

Once you have those, the formula depends on whether your greenhouse has rigid end walls (wood or metal) or flexible ends (plastic all around).

For rigid end walls:

Top and Sides Plastic = Length × (Arch Span + Overlap Allowance)

This covers the entire structure including both ends in one continuous piece of plastic.

End wall plastic:

If your ends are separate, calculate each like this:

End Wall Plastic = (Height + 1 ft) × (End Width + 1 ft)

Add 1 foot on each side to allow space for securing the plastic.

What Is the Best Thickness of Plastic for a Greenhouse?

The best plastic thickness depends on your climate and usage:

  • 6 mil is the most popular and recommended for most growers. It provides durability, UV protection, and lasts up to 4 years.
  • 4 mil is thinner and works for short-term or seasonal greenhouses, but not ideal for long-term use.
  • 8 mil or more is used in windy, snowy, or very hot conditions where stronger protection is needed.

If you're not sure, go with 6 mil. It offers a good balance between price, strength, and lifespan.

How Long Will 6 Mil Greenhouse Plastic Last?

6 mil greenhouse plastic can last up to 4 years if it’s UV-treated and properly installed. Without UV treatment, it may degrade in just 1–2 years under strong sunlight.

Will 4 Mil Plastic Work for a Greenhouse?

Yes, 4 mil plastic will work, but only for temporary or seasonal greenhouses. It’s not strong enough for year-round use or harsh weather. If you want lasting performance, especially through winter or strong sun, go with 6 mil or thicker.

How to Use the Greenhouse Plastic Calculator

Using our online tool is simple. Just follow these steps:

  1. Choose your unit system – feet or meters.
  2. Select your greenhouse type – rigid ends or flexible ends.
  3. Enter your greenhouse dimensions – length, height, arch span, and end width.
  4. Adjust the overlap allowance if needed (default is fine for most cases).
  5. Select your desired film thickness – 4, 6, or 8 mil.
  6. Click Calculate.

The calculator will show you the:

  • Total top + side plastic needed
  • End wall plastic size
  • Total area in your chosen unit system
  • Suggested film thickness

You can now confidently buy the exact amount of greenhouse plastic with no waste.

Final Verdict

Choosing the right greenhouse plastic doesn’t have to be a headache. With the Greenhouse Plastic Calculator, you can save time, money, and avoid mistakes. It helps you plan better and ensures your plants stay protected year-round.

Don’t just guess your measurements. Use the calculator and get your project started the smart way. Whether you're building a small backyard hoop house or a large commercial tunnel, this tool makes the process faster and easier.

FAQs

Can I use this calculator for any greenhouse shape?

Yes, it works best for tunnel, hoop, and standard arched greenhouses. For domes or custom shapes, manual adjustments may be needed.

What if my dimensions are in meters?

No problem. Just choose "metric" as your unit, and the calculator handles the rest.

How much plastic do I need for a 20×10 greenhouse?

With rigid ends: 20 × (10 + 3) = 20 × 13 = 260 sq ft, plus end wall plastic if needed.

Is UV protection included in the calculation?

No, but we recommend buying plastic labeled as "UV-stabilized" for better durability.

Where can I buy greenhouse plastic?

You can buy it from gardening stores, hardware outlets, or online from sites like Amazon or greenhouse suppliers.