Hammock Hang Calculator

How to use this hammock hang calculator

What this calculator does. This tool estimates the geometry of a symmetric hammock setup and the static forces associated with it. It turns anchor spacing, a target sit height, a measured hammock or ridgeline length, a selected hang angle, and the suspended load into a practical anchor height and suspension length. It also shows force components so you can see why very shallow strap angles create much larger loads. It is a planning aid, not a structural certification: it cannot inspect trees, walls, posts, straps, knots, carabiners, manufacturer load ratings, dynamic movement, wear, or local rules.

When to use it. It is useful when you are choosing between two candidate trees, setting fixed wall anchors, checking whether your straps have enough adjustment range, or comparing how a 15°, 30°, or 45° hang changes tension. A roughly 30° strap angle and a low sitting height are common starting points; REI's hammock camping setup guide describes the same practical starting geometry.

How to calculate. The calculator opens with a complete demonstration: 14 ft between anchors, an 18 in sit height, 175 lb in the hammock, a 9 ft ridgeline, and a 30° hang angle. Its example workbook is immediately available. To use your own setup:

1. Choose Unit system, then replace Distance between anchors, Preferred sit height, and Weight in hammock with your measurements.
2. Use Length to enter to tell the calculator whether your measured value is the Ridgeline length or Hammock length, then type that value in the length field.
3. Select a Hang angle. Read Anchor height and Suspension length first, then review the force cards and setup-detail table.
4. Use Display cord tension as to switch force reporting between pound-force and newtons. When the setup looks useful, choose Download Excel to export the current validated model. Reset clears the demonstration data; after Reset, the workbook button stays disabled until all required data is complete and valid again.

Input guide. Unit system is required and accepts Imperial or Metric; changing it converts current valid numeric entries rather than merely relabeling them. Distance between anchors is a positive decimal in feet or metres; 14 ft is the example. Increasing it usually raises the required anchor height and lengthens the suspension when the ridgeline is unchanged. Do not paste feet-and-inches punctuation or decimal-comma text. Preferred sit height is a nonnegative decimal in inches or centimetres; 18 in is the example and sits in the common chair-height range. Raising it raises the required anchor height by the same amount. Weight in hammock is a positive decimal in pounds or kilograms; 175 lb is the example. It drives the force results but not the geometry. If you want the load estimate to include a suspended pack or other gear, include that load consistently instead of interpreting this field as body weight only.

Length to enter is required and chooses the meaning of Ridgeline length/Hammock length. The length field is a positive decimal in feet or metres; the example ridgeline is 9 ft. A ridgeline must be shorter than the anchor spacing so each side has positive suspension run. When hammock length is selected, the model converts it to a ridgeline using the selected angle. Hang angle is required and offers 5°, 15°, 20°, 30°, and 45°. Lower angles reduce sag but rapidly increase horizontal and cord tension; higher angles do the opposite. Display cord tension as is required and changes only force units, not the underlying force.

Output guide. The top summary pills are quick mirrors of the detailed results: Angle repeats the selected Hang angle, Anchor height shows the attachment target, Suspension / side mirrors Suspension length for one side, and Cord tension mirrors the resultant force in that side. Anchor height is the estimated attachment height above level ground. Suspension length is the estimated strap/cord length from each hammock end to its anchor, excluding wrap length around a tree and hardware. Hammock length and Ridgeline length are paired geometry estimates from the selected angle. Cord tension is the resultant static force along each suspension side. Vertical tension / side is half the supported weight in the symmetric model. Horizontal tension / side is the inward pull associated with the suspension angle. Horizontal suspension run / side is the horizontal gap from a hammock end to its anchor. Suspension rise / side is the vertical rise from a hammock end to its anchor, while Hammock sag depth is the drop from the hammock-end line to the low point. In the setup-detail table, Measurement names the quantity, Value gives the current formatted result, and Meaning states what the quantity represents. These are estimates, not hardware ratings.

Worked example. With the startup values, the 9 ft ridgeline and 30° angle give an estimated hammock length of 10.4 ft. The 14 ft anchor spacing leaves 2.5 ft of horizontal suspension run on each side. Dividing that run by cos(30°) gives a suspension length of 34.64 in per side. The 30° geometry puts the anchors at 5.54 ft above level ground when the low point is 18 in high. For 175 lb, each side carries 87.50 lbf vertically; the resulting cord tension is 175.00 lbf and the horizontal component is 151.55 lbf.

Learn more. Geometry is only part of a responsible hang. Leave No Trace advises using live, sturdy trees and broad webbing; see its hammock camping impact guidance. Rules can also be site-specific: the National Park Service, for example, publishes hammock strap requirements for C&O Canal campgrounds. Check the rules for the exact land unit where you plan to hang.