What is Naismith's rule for estimating hike time?

Allow 20 minutes for each mile plus 30 minutes for every 1,000 feet of elevation gain. For 3 miles and 2,000 feet of climbing that gives exactly 2 hours. The planner adds a fast band and a conservative book-time band around it.

What is hiking 'book time' and why is it slower?

Book time uses roughly 30 minutes per mile plus 45 minutes per 1,000 feet of climb and 15 per 1,000 feet of descent. It approximates the pace of an average loaded party and is the estimate search-and-rescue groups recommend sharing as your ETA.

How do terrain, group and pack weight change the estimate?

The base time is multiplied by a terrain factor (good trail 1.0, rough trail 1.25, off-trail 1.5), a group factor (fit solo 1.0, mixed 1.15, family or beginners 1.3) and a pack factor (light 1.0, standard 1.08, heavy winter load 1.15). Planned rest minutes are added afterwards.

How does the daylight calculation work?

From your latitude and the day of year, the planner applies the Forsythe (1995) solar model: solar declination 0.4093 sin(2 pi N / 365 - 1.405) and day length = 24/pi acos((sin(-0.833 deg) - sin(phi) sin(delta)) / (cos(phi) cos(delta))). It warns when the conservative plan exceeds day length minus one hour.

Does descent count in hike time?

Classic Naismith ignores descent, so leave it at 0 to reproduce the textbook 3 miles plus 2,000 feet equals 2 hours vector. Steep, rough or knee-punishing downhills do cost time, so the planner optionally adds 5 to 15 minutes per 1,000 feet depending on the band.

Hike Time & Pace Planner徒步时间配速规划器

Naismith and Tobler with terrain, group and pack corrections — fast, normal and conservative estimates with ETAs and a daylight buffer. Naismith 与 Tobler 规则加地形、队伍与负重修正——快速、正常、保守三档用时，含到达时刻与天黑缓冲。

🧭 Weather & Navigation天气与导航求救 ⏱ Naismith · book time · ETANaismith · book time · 到达时刻 📅 Updated Oct 20262026 年 10 月更新

How the hike time calculator works

Most hikers underestimate the clock because they divide map distance by a flat-ground speed and ignore vertical gain. This planner starts from published walking rules, then adjusts for the ground, the group and the weight on your back — and finally checks the plan against available daylight.

Three bands, one trip

The normal band is the U.S. presentation of Naismith's rule: 20 minutes per mile plus 30 minutes per 1,000 feet of climb (and a modest 10 minutes per 1,000 feet of descent when you enter it). That is why the textbook vector works: 3 miles (60 minutes) plus 2,000 feet of climbing (60 minutes) equals exactly 2 hours. The fast band models a fit, unburdened party at 20 minutes per mile on the flat with 20 minutes per 1,000 feet of climb. The conservative band is traditional book time: 30 minutes per mile, 45 minutes per 1,000 feet of climb and 15 per 1,000 lost, matching the pace of an average loaded group that SAR statistics suggest is the honest number to give a waiting contact.

Multipliers and rest

Every elevation-adjusted base time is multiplied by terrain (good trail ×1.0, rough trail ×1.25, off-trail or scree ×1.5), group (fit solo ×1.0, mixed ability ×1.15, family or beginners ×1.30) and pack weight (light ×1.0, standard ×1.08, heavy winter load ×1.15). Your planned rest minutes are added only after the multipliers, and the start time produces an ETA for each band, flagged with “+1d” if it crosses midnight.

The daylight model

With latitude and date, the planner uses the Forsythe et al. (1995) astronomical model. Solar declination is δ = 0.4093·sin(2πN/365 − 1.405) in radians, where N is the day of year; day length is 24/π·acos((sin(−0.833°) − sinφ·sinδ)/(cosφ·cosδ)) hours, with a second run at −6° for civil twilight. At 45° latitude on June 21 (N = 172) this returns about 15.6 hours. The verdict turns to a warning whenever conservative book time exceeds day length minus a one-hour buffer — the margin that keeps a slow finish from becoming a benightment callout.

徒步时间是怎么算出来的

多数人低估用时，是因为只用地图距离除以平路速度，忽略了海拔爬升。本规划器以公开的行进规则为起点，再按地面状况、队伍构成和背负重量修正，最后把计划与当天白昼长度对照。

一次行程，三档估计

正常档是美式 Naismith 规则：每英里 20 分钟 + 每 1000 英尺爬升 30 分钟（填写下降时另加每千英尺 10 分钟）。所以教科书向量精确成立：3 英里（60 分钟）+ 2000 英尺爬升（60 分钟）= 整 2 小时。快速档模拟健壮轻装队伍：平路每英里 20 分钟、每千英尺爬升 20 分钟。保守档即传统 book time：每英里 30 分钟、每千英尺爬升 45 分钟、下降 15 分钟，最接近普通负重队伍的实际速度，也是搜救机构建议你报给联系人的 ETA。

修正系数与休息

含爬升的基础时间统一乘以地形系数（良好步道 ×1.0、崎岖步道 ×1.25、无路/碎石 ×1.5）、队伍系数（壮汉独行 ×1.0、混合 ×1.15、亲子/新手 ×1.30）与负重系数（轻装 ×1.0、标准 ×1.08、冬季重装 ×1.15）。计划休息分钟数在系数相乘之后再加入；出发时间会为三档分别算出到达时刻，跨过午夜时标注“+1 天”。

昼长天文模型

打开天黑检查后，按纬度与日期使用 Forsythe 等（1995）模型：太阳赤纬 δ = 0.4093·sin(2πN/365 − 1.405)（弧度，N 为年内第几天）；昼长 = 24/π·acos((sin(−0.833°) − sinφ·sinδ)/(cosφ·cosδ)) 小时，并用 −6° 再算一次民用晨昏蒙影时长。北纬 45°、6 月 21 日（N=172）昼长约 15.6 小时。当保守档用时超过昼长减 1 小时缓冲时，结论转为警告——避免慢队摸黑、被迫求救。

Frequently asked questions常见问题

What is Naismith's rule?什么是 Naismith 规则？

Allow 20 minutes per mile plus 30 minutes per 1,000 feet of climbing. The classic vector — 3 miles and 2,000 feet of gain — therefore takes exactly 2 hours before any terrain, group or pack adjustment.每英里 20 分钟，另加每 1000 英尺爬升 30 分钟。经典向量“3 英里 + 2000 英尺爬升”在任何修正之前恰好等于 2 小时。

Why does the planner give three different times?为什么给出三个不同时间？

Fast, normal (Naismith) and conservative (book time) bracket your real pace. Report the conservative number as your ETA and keep the fast number as a turnaround benchmark.快速、正常（Naismith）、保守（book time）三档框住真实配速区间。把保守时间报给联系人，把快速时间当作折返基准。

Should I count downhill time?下坡要算时间吗？

Classic Naismith ignores descent (set it to 0 for the textbook vector). Steep, loose or talus descents genuinely slow loaded parties, so the planner lets you add 5–15 minutes per 1,000 feet by band.经典 Naismith 不计下降（教科书向量填 0）。但陡峭、松动、碎石坡对负重队伍确实费时，本工具允许按档位每千英尺加 5–15 分钟。

How accurate is the daylight formula?昼长公式准吗？

The Forsythe (1995) model is accurate to a few minutes for flat horizons away from the poles. Mountain horizons, valley shade and weather shorten the usable light — which is exactly why the planner reserves a one-hour buffer.Forsythe（1995）模型在两极之外、地平线平坦时误差仅几分钟。山脊遮挡、峡谷阴影与天气都会缩短可用白昼——这正是预留 1 小时缓冲的原因。

What do I do when the plan runs into darkness?计划要走到天黑怎么办？

Start earlier, shorten the route, or require a headlamp (with spare batteries) for every person. Fix a clock-time turnaround, not just a map point, and leave the conservative ETA with an emergency contact.更早出发、缩短路线，或要求每人带头灯（含备用电池）。按钟点而非仅按地点设定折返时间，并把保守档 ETA 留给紧急联系人。