What R-value sleeping pad do I need?

For UK summer camping (ground temp 10°C+), R1-2 is fine. Three-season use needs R2.5-3.5. Winter camping below freezing requires R4-5. Stacking two pads adds their R-values together, so a foam pad (R1.5) under an inflatable (R3) gives R4.5.

What is R-value and why does it matter?

R-value measures thermal resistance - how well the pad insulates you from the cold ground. Ground contact draws heat from your body much faster than cold air (conduction vs convection). A sleeping bag loses most of its insulation underneath you because your body compresses the fill.

Is ground temperature the same as air temperature?

No. Ground temperature is usually different from air temperature. In winter, frozen ground can be -5 to -15°C even when air is around 0°C. In summer, ground retains warmth and may be 10-15°C even on cool nights. Snow actually insulates - snow-covered ground is often warmer than exposed frozen ground.

Do R-values stack when using multiple pads?

Yes. Since the ASTM F3340-18 testing standard was introduced, R-values are additive. A closed-cell foam pad (R1.5-2.0) under an inflatable pad (R3.0) gives a combined R4.5-5.0. This is a common and weight-effective strategy for winter camping.

CampCalcs

Sleeping Pad R-Value Calculator

Calculate the required sleeping pad R-value from expected ground and air temperatures.

Expected Ground Temperature

Ground surface temperature where you will sleep

Expected Air Temperature

Overnight low air temperature

I am a cold sleeper (adds R1.0 safety margin)

How We Calculate This

The calculator estimates required R-value primarily from ground temperature, with adjustments for air temperature and personal warmth preference.

Formula

Required R = (10 - Ground temp) / 3 + Air temp adjustment + Cold sleeper bonus

R-value guide

R1-1.5: Summer only (ground 10\u00B0C+)
R2-3: Three-season (ground 2-10\u00B0C)
R3-5: Winter (ground -10 to 2\u00B0C)
R5-7: Cold winter / mountain (ground -20 to -10\u00B0C)
R7+: Expedition / extreme cold

Frequently Asked Questions

Related Calculators

Tent Footprint Calculator

Calculate the ground area and footprint dimensions for your tent setup.

Tarp Size Calculator

Determine the right tarp size for your shelter configuration and number of occupants.

Hammock Hang Calculator

Calculate the ideal hang angle, ridge line length and tree distance for your hammock.

Ground Pad R-Value Calculator

Calculate combined R-value when stacking sleeping pads for cold weather camping.

Sleeping Pad Calculator

Find the right sleeping pad size and type based on your height, width and conditions.

Last updated: March 2026

All calculations are estimates. Always verify conditions and use proper safety equipment outdoors.