Measure bumper-to-bumper length, maximum width with the mirrors in their storage position, and height down to the tie-down line. Add drop on both sides and both ends. A generic tarp can protect a parked car for a short stretch. A soft, snug, breathable fitted cover is the better daily outdoor cover.
The usual failures are buying by “sedan” or “SUV” as if those were sizes, then leaving a loose sheet that grinds grit into the paint.
Generic tarp vs fitted car cover
A rectangular tarp is a fast weather shell. It does not know where your mirrors, antenna, spoiler, roof rack, or hitch sit. A fitted car cover is cut for those points and often has a softer inner face. Use a tarp for a storm, a trip, or a few days in the driveway. If the car will live outdoors for months, a fitted cover is the product that was designed for paint.
How to measure
- Park on level ground. Fold in mirrors only if you will store them folded under the cover.
- Measure bumper-to-bumper length, including a spare-tire carrier or hitch if it stays on.
- Measure the widest point with a level tape. On most cars that is mirror to mirror.
- Measure from the highest point (roof, light bar, rack, box) down to the line where you want the cover to end: wheel arch, rocker, or ground.
- List attachments that stick out of that box: antenna, roof rack, snorkel, bed rack, toolbox, bike rack.
- Add front, rear, left, and right drops so the sheet can tie under or around the body. Drops do not have to match if one end has a hitch or a winch.
Planning formulas
Minimum tarp length = overall length + front drop + rear drop
Minimum tarp width = max width (mirrors in) + left drop + right drop
A 16 ft sedan that is 6 ft 2 in wide with mirrors, covered 18 in down from the roof line on every side, needs about 19 ft by 9 ft 2 in. A 20×12 ft stock sheet is the first common size that clears both numbers. Covering the same car to the ground would add two full heights and produce a much larger, heavier sheet that is harder to keep from flapping.
Run the numbers in the tarp size calculator (3D Object mode) if you want the stock-size round-up done for you. The Plan Builder uses the same equipment-cover geometry if you also want a fabric and weight check from one set of measurements.
Measurement worksheet
| Item | Where to take it | Your value |
|---|---|---|
| Overall length | Bumper to bumper, hitch or carrier on if it stays | _____ ft _____ in |
| Max width | Mirror to mirror in the storage position | _____ ft _____ in |
| Height to cover line | Highest point down to wheel arch, rocker, or ground | _____ ft _____ in |
| Front / rear drops | How far the sheet must reach past each bumper | _____ / _____ in |
| Left / right drops | How far past each side, including mirrors | _____ / _____ in |
| Attachments | Antenna, rack, box, light bar, toolbox, bike rack | ________________ |
| Pad list | Mirror housings, antenna, rack feet, sharp trim | ________________ |
Starting-point stock classes after you do that math, not instead of it:
| Vehicle | What usually grows the outline | Common stock starting range |
|---|---|---|
| Compact / sedan | Mirrors; optional roof rack | Often 20×12 to 20×20 ft class |
| SUV / crossover | Height, width, roof rails | Often 20×20 to 20×30 ft class |
| Pickup | Length, mirrors, bed rack or toolbox | Measure; length grows fast |
Paint, grit, and flap
Covercraft’s paint article is blunt: dirt or debris trapped between the cover and the car acts like sandpaper, and a cover that moves in the wind rubs the finish. Their checklist is wash the car first, use a snug cover, keep the cover clean, and avoid covering a wet car (moisture under a cover can leave water spots or dulling).
A generic PE tarp is a worse inner surface than a fitted cover. Pad mirror housings, antennas, rack feet, and sharp trim. Tension the sheet so it cannot flap. Do not use a tarp as a substitute for washing off sap or bird droppings that are already on the paint.
Ventilation and moisture
Covercraft states that its car-cover fabrics “are not waterproof — they are breathable to allow moisture, condensation and heat to escape from under the fabric.” That is the design intent of a purpose-made cover. A coated PE tarp is the opposite construction: it sheds rain and also traps vapor against glass, rubber, and paint.
If you use a tarp anyway, give moisture a way out. Do not wrap the car to the ground on a damp day and walk away for a month. Dry the car and the sheet before long storage. A fitted, breathable cover is the product that was built for that job.
Paint and fit: Covercraft, “Will My Car Cover Scratch My Paint?”. Breathability: Covercraft Automotive Warranty (“Materials are not waterproof — they are breathable to allow moisture, condensation and heat to escape from under the fabric.”). Those statements describe Covercraft’s own covers, not generic PE tarps.
Frequently asked questions
Is a tarp good enough as a car cover?
For short-term outdoor protection, yes. For daily outdoor storage, a softer custom-fit car cover usually reduces chafe and fits mirrors and antennas better than a stiff generic tarp. Purpose-made covers are also built to let moisture vapor out; a PE tarp is not.
What size tarp do I need for a sedan?
Compute it: bumper-to-bumper length plus two end drops, and maximum width including mirrors plus two side drops. Many sedans land near a 20×12 to 20×20 ft stock sheet once you add those drops, but trim, racks, and how far down you cover change the outline. Measure the car.
Will a tarp scratch my paint?
It can. Covercraft’s paint guidance is that grit trapped under a cover acts like sandpaper, and a cover that flaps in wind rubs the finish. Wash the car, use a clean cover, pad contact points, and keep the sheet taut. A rough industrial tarp is a worse inner surface than a soft fitted cover.
Should I cover a car completely to the ground?
Full coverage helps weather protection, but you still need secure tie-downs and a way for moisture to leave. A cover that balloons in wind can damage mirrors and paint. A drop to the wheel line is often enough for a temporary tarp if you can tie under the body.
Can I drive with a tarp on the car?
No. Tarps and casual covers are for parked storage only.
How this guide was prepared
We separate geometry and unit conversions from product claims, use exact standards where available, and flag specifications that vary by manufacturer. See our editorial policy for the review process.