Solar Cover Thickness: 8, 12 or 16 Mil for Your Pool
For most backyard pools, a 12-mil solar cover is the safe middle choice. Go to 16 mil if your pool sits in a cooler or windy spot and you can handle a heavier cover. Go to 8 mil if your climate is mild and you want the lowest price and the lightest load. Thickness is only one part of the decision, so below we walk through what the number means, what you gain and give up at each step, and how to choose.
TL;DR
- Thickness is measured in mils. One mil is a thousandth of an inch, so a 12-mil cover is 0.012 inch thick.
- 8 mil is the lightest and cheapest. 12 mil balances weight and durability. 16 mil holds heat and lasts longer but is heavier and bulkier.
- Cooler or windy climates favor 16 mil. Mild or warm climates do fine with 8 mil.
- Thicker is not automatically better. Size, fit, UV protection and how you will store the cover matter just as much.
Table of Contents
- What a mil actually measures
- 8 mil vs 12 mil vs 16 mil
- How much does thickness change pool temperature?
- Durability: what wears a cover out
- What to weigh besides thickness
- A quick way to decide
- Pool care essentials from PriceLows™
- Our perspective
- FAQ
- Sources
What a mil actually measures
A mil is one thousandth of an inch. Solar pool cover thickness is measured in mils, and retail covers generally run from 8 to 16. If you see numbers in microns instead, the conversion is simple: one mil is about 25.4 microns, so 12 mil is roughly 305 microns and 16 mil is roughly 406 microns.
Most solar covers are bubble sheets: two layers of polyethylene with air pockets between them. The mil figure describes the film. It does not tell you the bubble size or the UV treatment, which is why two covers with the same rating can behave differently.
8 mil vs 12 mil vs 16 mil
Here is how the three common thicknesses compare in practice.
| 8 mil | 12 mil | 16 mil | |
|---|---|---|---|
| Weight | Lightest | Moderate | Heaviest |
| Price | Lowest | Moderate | Highest |
| Heat retention | Adequate in warm weather | Good | Best |
| Durability | Shortest wear life | Solid all-rounder | Longest wear life |
| Handling | Easy for one person | Manageable | Harder, bulky to store |
| Best climate | Mild or warm | Most regions | Cool or windy |
The general pattern holds across published guides: 16-mil models generally offer superior durability and heat retention compared with thinner covers, while the 12 to 14 mil range keeps good heat retention and stays relatively easy to handle.
When 8 mil makes sense
A thin cover suits a small or mid-size pool in a warm region where nights stay mild. It is easy to pull on and off by yourself, and it costs the least. The tradeoff is a shorter life, since thinner film tears and breaks down sooner under sun and pool chemicals.
When 12 mil is the right call
This is the pick for most homeowners. It is stiff enough to resist snags and wind flapping, light enough that one adult can fold it, and priced between the extremes. If you are undecided, start here.
When 16 mil earns its extra cost
16-mil covers are recommended for cooler climates or windy conditions. They suit shoulder-season swimming, pools that get a lot of foot traffic around the edge, and owners who want to buy once and keep it for years. The downsides are real: thicker covers are heavier, harder to handle and bulky when folded. On a large pool, a wet 16-mil sheet is a two-person job unless you use a reel.
How much does thickness change pool temperature?
Less than most people expect. The cover does two jobs: it traps solar heat, and it stops evaporation. Evaporation is the bigger one. The U.S. Department of Energy notes that evaporation is the primary source of energy loss in pools, and covers can cut heating costs by 50% to 70%.
Thickness helps at the margin. Thicker covers typically perform better at retaining heat and preventing evaporation, and in hands-on testing, solar covers raised water temperature by about 4°F to 5°F in favorable sun. That gain comes mainly from having a cover on the water at all. Going from 12 to 16 mil adds a smaller step on top. If you want the full money picture, see our piece on whether solar pool covers really save you money.
Durability: what wears a cover out
Thickness slows wear, but it is not the only factor. Pool sanitizers attack the film. One manufacturer guide explains that thicker material gives oxidizing agents more polymer to break down over time, which is one reason heavier covers outlast light ones. Still, a cover that is left in direct sun while the water is heavily shocked can fail early at any thickness.
Three habits protect any cover:
- Remove or fold it back before you shock the pool, and let the water settle before it goes back on.
- Do not leave it baking on the deck. Heat and UV on the deck are harder on it than the pool water.
- Store it rolled loosely, clean and dry, out of direct sun.
What to weigh besides thickness
A mil rating is a convenient comparison tool, not a quality guarantee. For bubble-style covers, mil thickness is the most common retail specification, but it is not a direct substitute for judging overall quality. Check these as well:
- Size and fit. Buy to the water surface, not the pool’s outer dimensions. Trim the cover to the shape of the water, a few inches smaller all around.
- UV stabilization. A UV-treated film holds up far longer than an untreated one of the same thickness.
- Bubble design. Bubble geometry affects both heat transfer and strength, which is why thickness alone cannot pick the best cover for every pool.
- Your own strength and setup. Be honest about who will be pulling the cover on and off every day, and whether you will use a reel.
- Color. Clear covers let light pass into the water. Blue or dark covers absorb more at the surface. Both work, so match the color to how you use the pool.
A quick way to decide
Ask yourself three questions.
- How long is your swim season? A short season in a cool region points to 16 mil. A long, warm season points to 8 or 12.
- Who handles the cover? If one person does it daily on a big pool, pick 12 mil or lighter, or add a reel.
- Do you want to replace it often? If you would rather pay more once, take the thicker film. If you would rather keep upfront cost down, 8 or 12 mil is fine.
Pool care essentials from PriceLows™
A cover is one piece of a pool that is cheap to run. At PriceLows™ we stock affordable gear across Pool & Spa, Lawn & Garden and Outdoor Furniture, with free shipping on most orders and a 100% shipping protection plan. If you are setting up a shaded lounge area next to the pool or protecting plants nearby, our sunshade nets are one budget-friendly place to start, and you can browse the rest of our pool and spa range.
For smaller jobs, a pool mesh strainer for hot tubs and spas keeps filter cartridges protected.
Our perspective
We have spent 15 years helping families spend less on the home, yard and garage, and the pattern with pool gear is the same as with everything else: the most expensive option is rarely the one that saves you money. A 16-mil cover that is too heavy to lift gets left off the pool, and a cover that stays off saves nothing. We would rather see you buy the 12-mil cover you will use every evening than the 16-mil cover that sits folded in the garage.
Our rule of thumb is to match the cover to the person who will handle it, then to the climate, and only then to the price. Thickness is the easiest number to compare, but fit and daily habit decide whether a cover pays for itself.
— Thane Holland
FAQ
How many mils should a solar pool cover be?
Twelve mil suits most pools and most owners. Choose 8 mil for mild or warm climates and tight budgets, and 16 mil for cooler or windy locations where you want maximum durability and heat retention.
Is a 16-mil solar cover worth it over 12 mil?
It can be, if you have a cool climate, a long season or you want the longest-lasting film. You pay for it in weight and bulk, so it is a poorer fit if one person must handle a large cover alone.
What are the downsides of a thicker solar cover?
Thicker covers are heavier, harder to fold and take up more storage space. They also cost more. If handling is a chore, the cover is likelier to stay off the water.
Does a thicker cover warm the pool faster?
Somewhat. Thicker covers generally hold heat and block evaporation better, but the biggest gain comes from using any cover consistently. Sun exposure, wind and water volume have a large effect too.
Sources
- The 7 Best Solar Pool Covers of 2026, Tested and Reviewed
- The 5 Best Solar Pool Covers, According to Our Tests
- Pool efficiency fact sheet, U.S. Department of Energy Better Buildings Solution Center
- Guidance for pool cover sizing
- Pool Cover Thickness Chart
- Solar Bubble Pool Covers: 400 vs 500 vs 600 Micron