Does total height decide my backpack size?

No — torso length does. Measure from the prominent C7 vertebra at the base of the neck (chin tilted forward) straight down the spine to the iliac crest, the bony shelf on top of the hip bones. Common bands are XS under 43 cm, S 43–47.9 cm, M 48–52.9 cm, L 53 cm and up, but always compare with the manufacturer’s own size chart.

What pad R-value do I need?

R-value measures ground insulation: about R2 for warm summer nights, R3.5 for three-season use, R4.5 around freezing and R5.5 or higher for winter camping. A high-loft bag on a thin pad still loses most heat to the ground. Stacking two pads adds their R-values.

EN COMFORT, LIMIT or EXTREME — which sleeping bag number do I plan to?

Plan to the EN 13537 / ISO 23537 COMFORT rating — the temperature a standard woman can sleep comfortably at. LIMIT is a shivering-man boundary and EXTREME is a survival number with hypothermia risk; never plan around either. Choose a bag whose COMFORT rating is at least 5 °C colder than your forecast overnight low to keep a margin.

Why does the tool want a 5 °C safety margin on the sleeping bag?

Lab ratings assume a rested, well-fed person on an adequate pad in still air. Real nights include moisture in the insulation, wind, fatigue, altitude and metabolism differences. A bag rated 5 °C below the coldest forecast night absorbs those losses instead of discovering them at 3 a.m.

Gear Fit Advisor装备适配顾问

Trekking-pole length, pack torso size, sleeping-pad R-value and bag comfort rating. 登山杖长度、背包躯干尺码、睡垫 R 值与睡袋舒适温标，一次算清。

📏 Trip & Gear行程与装备 📅 Updated Oct 20262026 年 10 月更新

How the gear fit advisor works

Three of the most expensive backpacking mistakes are sizing mistakes: poles that lock your shoulders at the wrong angle, a pack that fits someone else’s spine, and a sleep system rated for a colder-looking number that is not the number you should trust.

Trekking poles: the 90° elbow rule

For level ground the advisor uses the established approximation:

L (cm) = round(height (cm) × 0.66)

A 175 cm hiker therefore starts at about 116 cm (roughly 46 in). The geometry behind the shortcut is the real fit test: stand relaxed on flat ground with the pole tip beside your foot; your forearm should be horizontal and the elbow flexed to about 90°. On long uphills shorten by roughly 5–8 cm for leverage and an upright wrist; on long downhills lengthen by about 5 cm to stay upright without reaching.

Pack sizing: torso, not total height

Pack suspension is sized to the torso. Locate the C7 vertebra by tilting your chin forward and finding the prominent knob at the base of the neck; locate the iliac crest — the bony shelf on top of the hip bones. A soft tape from C7 down the relaxed spine gives torso length. The advisor maps it to conventional bands: XS under 43 cm, S 43–47.9 cm, M 48–52.9 cm, and L at 53 cm and up. Manufacturers’ charts vary, so treat the band as the starting point and verify with a loaded try-on: the hip belt must wrap the top of the hip bones, not the waist.

Sleep system: R-value plus EN ISO 23537

Pad insulation follows typical R-value bands: R≈2 for warm summer nights, R3.5 for three-season use, R4.5 near freezing and R5.5+ for winter. Heat loss to the ground is conductive — a warm bag cannot fully compensate for a thin pad, and two pads stack their R-values. Sleeping bags are rated under EN 13537, now EN ISO 23537, which reports three numbers. Plan only to the COMFORT rating (standard woman sleeping comfortably); LIMIT is a shivering boundary and EXTREME a survival mark. The selection rule is:

bag COMFORT ≤ forecast overnight low − 5 °C

The 5 °C margin pays for moisture loft loss, wind, fatigue, altitude and individual metabolism — and for cold sleepers, women and anyone under 16, add even more.

计算原理

背包装备最昂贵的三类错误都是尺码错误：登山杖角度不对锁死肩膀、背包贴合了别人的脊柱、以及信了睡袋上那个“看起来更冷”但不该参考的数字。

登山杖：90° 肘部法则

平地杖长采用成熟的经验近似：

L（厘米）= 四舍五入（身高厘米 × 0.66）

175 cm 徒步者因此从约 116 cm（约 46 英寸）起步。该经验式背后的几何关系才是真正校验标准：平地放松站立、杖尖落在脚边时，前臂应水平、肘角约 90°。长上坡缩短约 5–8 cm 以改善发力；长下坡加长约 5 cm，身体保持直立、不用俯身够杖。

背包尺码：看躯干不看总身高

背包背负按躯干长度分码。下巴前低，找到颈后最突出的 C7 椎骨；再找到髋骨上方的骨性平台髂嵴。软尺从 C7 沿放松状态的脊柱量到髂嵴即躯干长。尺码带为：XS 小于 43 cm、S 43–47.9 cm、M 48–52.9 cm、L 53 cm 及以上。各厂尺码表有差异，结果仅作起点，必须负重试背确认：腰带要包住髋骨上方而不是腰。

睡眠系统：R 值 + EN ISO 23537

睡垫隔热按典型 R 值带：暖夏约 R2、三季 R3.5、近冰点 R4.5、冬季 R5.5 以上。地面导热流失无法靠更暖的睡袋完全弥补，两块垫叠用 R 值相加。睡袋按 EN 13537（现 EN ISO 23537）给出三个温标，只应按 COMFORT（舒适） 规划——标准女性可舒适安睡的温度；LIMIT 是发抖边界，EXTREME 是带失温风险的生存标记。选择规则：

睡袋 COMFORT ≤ 预报夜间最低温 − 5 °C

这 5 °C 余量用于补偿潮湿导致的蓬松度下降、风、疲劳、高海拔与个体代谢差异；怕冷者、女性与未成年人建议再留更多。

Frequently asked questions常见问题

How long should my trekking poles be?登山杖该调多长？

About height × 0.66 in cm (175 cm → 116 cm), but verify the 90° elbow posture on flat ground. Shorten 5–8 cm uphill, lengthen ~5 cm downhill.约为身高（厘米）×0.66（175 cm → 116 cm），但须用平地 90° 肘角校验。上坡缩 5–8 cm，下坡加约 5 cm。

Does total height decide backpack size?背包尺码看总身高吗？

No — torso length from C7 to the iliac crest decides: XS <43 cm, S 43–47.9, M 48–52.9, L ≥53. Check the maker’s chart and try it loaded.不看总身高，看 C7 到髂嵴的躯干长：XS <43、S 43–47.9、M 48–52.9、L ≥53 厘米。再对照厂商尺码表负重试背。

Which pad R-value do I need?睡垫需要多少 R 值？

R2 summer, R3.5 three-season, R4.5 near freezing, R5.5+ winter. A great bag cannot replace pad insulation; stacked pads add R-values.夏季 R2、三季 R3.5、近冰点 R4.5、冬季 R5.5 起。睡袋再好也替代不了睡垫隔热；两垫叠用 R 值相加。

Which sleeping bag temperature number matters?睡袋该看哪个温标？

The EN ISO 23537 COMFORT rating only — never LIMIT or EXTREME. It should be at least 5 °C below your coldest forecast night.只看 EN ISO 23537 的 COMFORT 舒适温标，绝不按 LIMIT/EXTREME 规划；它应比最冷预报夜再低至少 5 °C。

Why require a 5 °C margin?为什么要留 5 °C 余量？

Lab ratings assume rested people, adequate pads and still air. Moisture, wind, fatigue, altitude and metabolism steal warmth; the margin absorbs that.实验室温标假设人已充分休息、睡垫足够、无风。潮湿、风、疲劳、海拔与代谢差异都会偷走热量，余量就是为此而留。