Two small tools, both for the moment you are choosing gear or setting up camp. The first suggests a sleeping pad R-value for your conditions. The second checks how hard a hammock pulls on its straps and anchors. Both run entirely in your browser: nothing you type is sent anywhere.
Pick a sleeping pad R-value
Enter your conditions and press Pick an R-value. Your result will appear here.
R-value measures a pad's resistance to heat flow, and higher means more insulation. Most pads are tested to the ASTM F3340 standard, so compare ratings from different makers. This picker uses common rule-of-thumb bands, and your own comfort, your sleeping bag or quilt and the weather all matter.
Hammock hang-angle check
Enter your numbers and press Check the hang. Your result will appear here.
This uses a simple straight-line model (tension per side = weight ÷ (2 × sin of the angle)). It ignores stretch, the hammock's own weight and shock loads, so treat it as an estimate and follow the ratings and instructions for your hammock, straps and anchors.
How the pad picker works
R-value is a measure of a pad's resistance to heat flow, so a higher number means more insulation from the cold ground. Most pads are tested using the ASTM F3340 standard, which makes ratings comparable between makers, though a rating on a label is a lab result and not a guarantee of how warm you will feel.
The picker starts from your coldest expected night temperature and maps it to a commonly cited band:
- Summer: about R1 to 3.
- Three-season: about R3 to 5.
- Winter: R5 and up, and for very cold nights, R6 or more.
Those bands are guidelines, not laws, and different makers draw the lines in slightly different places. The picker then nudges the range up if you sleep cold or if the ground is cold, damp or snowy, and down if you sleep warm. Trip style changes the advice, not the number: if you are backpacking, you will weigh warmth against pack weight.
Stacking pads
When you place one pad on top of another, their R-values roughly add. A thin closed-cell foam pad under an inflatable pad is a classic winter solution because it adds insulation, protects the inflatable pad from punctures and gives you a backup if the inflatable fails. Read the sleep system guide for the full picture.
How the hammock check works
A hammock does not hang like a rope pulled tight. It sags, and the sag creates an angle between the hammock's suspension and the horizontal. The flatter the hang, the more force each side carries. The tool uses simple geometry:
- Angle = arctangent of (sag ÷ half the distance between anchors).
- Force per side = total weight ÷ (2 × sin of the angle).
At an angle of 30 degrees, the force on each side is equal to the total weight in the hammock. At 15 degrees, it is nearly double. That is why a flat hang is a common mistake. Many hammock guides suggest an angle of roughly 25 to 35 degrees, which is the range the tool uses. See our hammock category page for suspension, straps and stands.
Protecting trees
The Leave No Trace Center for Outdoor Ethics recommends hammock straps at least one inch wide, hanging below about five feet, using trees at least about six inches in diameter, and camping at least 200 feet from water. Those numbers are guidance and some campgrounds and land managers ban hammocks on trees, so check the rules where you are going. Where trees are not an option, a free-standing hammock stand is an alternative.
Limits of these tools
The pad picker cannot know how warm you will feel. It does not account for wind, humidity, your sleeping bag or quilt, your clothing, your food or your health. The hammock model assumes a straight-line V shape, ignores the weight of the hammock itself and cannot account for stretch or dynamic loading. If a result looks odd, trust the manufacturer's instructions and your own judgment.
Frequently asked questions
What R-value do I need for 30°F?
Many guidelines put it at R5 or higher. If you sleep cold or the ground is cold or damp, aim for the higher end or stack a foam pad under it.
Is a higher R-value always better?
It is warmer, but it can be heavier and bulkier, and in hot weather it may feel too warm. Choose the lowest rating that keeps you comfortable.
Do R-values add up when I stack pads?
Roughly, yes. Combining two pads gives a total close to the sum of their R-values.
Does this tool save or share my numbers?
No. The calculations happen in your browser and nothing is stored or sent.
What hang angle should I use for a hammock?
Many guides suggest about 25 to 35 degrees. Flatter hangs put much more force on the anchors.
