Frost Cloth Coverage Calculator

Frost Cloth (also called row cover or garden fleece) protects plants from frost damage by trapping heat radiating from the soil.
Proper sizing includes drape allowance so the cloth reaches the ground on all sides.

Formula:

Cloth width = Bed width + (2 × Plant height) + (2 × Drape)
Cloth length = Bed length + (2 × Plant height) + (2 × Drape)
Total area = Cloth width × Cloth length

Where Drape is the extra material needed to reach the ground and be secured (typically 6–12 inches / 15–30 cm on each side).

Plant height is added to both dimensions, not just the width. The sheet has to climb over the plants and come back down to the soil at the two ends of the bed as well as along the sides. Skip that and you buy a piece that sits neatly across the middle and leaves both ends open, which is where the cold air walks in.

Frost Cloth Weights:

Those figures are what the Agribon grades of those weights are sold to, and they come from a few degrees of warmth held over the soil (about 4°F for the lightest, 8°F or more for the heaviest). Below about 24°F no cloth alone will do it. Add a second layer on hoops, or bring the plants in.

Standard Roll Sizes:

• Common widths: 6 ft (1.8 m), 10 ft (3 m), 12 ft (3.7 m)
• Rolls typically come in 25, 50, or 100 ft (7.6, 15.2, 30.5 m) lengths

Practical Example:

A raised bed 4 ft × 8 ft (1.2 m × 2.4 m) with 18-inch (45 cm) tall plants and a 9-inch (0.75 ft) drape:

• Cloth width: 4 + (2 × 1.5) + (2 × 0.75) = 8.5 ft (2.59 m)
• Cloth length: 8 + (2 × 1.5) + (2 × 0.75) = 12.5 ft (3.81 m)
• Total area: 8.5 × 12.5 = 106.3 sq ft (9.9 m²)

A 10 ft wide roll covers that 8.5 ft width with room to spare. Buy the 25 ft length and you have enough for two of these beds.

Metric/Imperial Conversions:

• 1 yard = 0.914 m = 3 ft
• 1 sq yard = 0.836 m² = 9 sq ft

Tips:

• Secure edges with stones, soil, or garden staples to prevent wind from lifting the cloth.
• Lightweight covers can rest directly on plants. Heavy covers may need support hoops.
• Remove covers during the day for sun exposure and pollinator access (unless temperature stays below freezing).
• Frost cloth can be reused for several seasons if stored dry.
• For individual plants, calculate the circumference and height to size a plant wrap instead.
• Water the soil before covering. Moist soil releases more heat overnight.