Passage Planning
A thorough passage plan is both a legal requirement under SOLAS and the mark of good seamanship. This guide walks you through the complete process — from initial appraisal to monitoring at sea.
What Is Passage Planning?
Passage planning is the systematic process of preparing for a voyage before you leave the dock. Under the International Convention for the Safety of Life at Sea (SOLAS), all vessels — from supertankers to small yachts — are required to plan their voyages.
But beyond the legal requirement, passage planning is simply how you avoid getting caught out. A 30-minute session with a chart, tide tables, and a weather forecast can prevent hours of misery — or worse — at sea.
Even for short day sails, a basic passage plan should cover: weather check, tidal heights at departure and arrival, any hazards on the route, and a "what if it goes wrong" fallback plan.
The 4 IMO Stages
The International Maritime Organization defines four stages of passage planning. For yacht sailors, the same framework applies — just scaled to your vessel.
1. Appraisal
Gather all the information you need before you start planning.
- Check charts for the route — up-to-date, correct scale
- Review pilot books and sailing directions for the area
- Check Notices to Mariners for any recent changes
- Assess weather forecasts for the passage window
- Review tidal information — heights and streams
- Note any TSS, restricted areas, or military exercise zones
- Consider the crew's experience and condition
2. Planning
Plot the route and make the decisions.
- Plot waypoints on the chart (paper or electronic)
- Note course and distance for each leg
- Identify hazards along the route and safe passing distances
- Calculate ETAs based on expected speed
- Plan departure time to optimise tidal streams
- Identify bolt holes — safe harbours along the route
- Set abort criteria (wind speed, sea state, visibility)
- Calculate fuel requirements with reserves
3. Execution
Put the plan into action — but stay flexible.
- Brief the crew before departure
- Follow the planned route and waypoints
- Log position fixes at regular intervals
- Maintain a proper lookout at all times
- Be ready to deviate if conditions change
- Monitor weather throughout the passage
4. Monitoring
Continuously check your progress against the plan.
- Compare actual position to planned position
- Check if ETAs are realistic — are you ahead or behind?
- Monitor weather changes — compare to forecast
- Watch for set and drift from tidal streams or current
- Decide early if you need to use a bolt hole
- Update the plan if conditions require it
Weather Assessment
Weather is the single biggest variable in any passage. Check multiple sources and understand the models behind them.
48 hours before
Get the big picture. Check synoptic charts, frontal systems, and the general weather pattern. Look at 5-day forecasts on Windy using ECMWF. Is there a weather window or is it deteriorating?
24 hours before
Narrow your focus. Check the inshore waters forecast, the shipping forecast, and compare models. Look at wind, swell, and visibility. Check WindFinder for departure point conditions.
Morning of departure
Final check. Has anything changed? Compare actual station data with forecasts. If the forecast and reality already disagree, respect reality. Look out of the porthole — does the sky match the forecast?
Rule of thumb:If in doubt, don't go out. There will always be another weather window. There won't always be another you.
Tidal Planning
In tidal waters, getting the tide right can halve your passage time or double it. There are two aspects to consider: tidal heights and tidal streams.
Tidal Heights
How deep is the water at a given time? Calculate the height of tide at your departure and arrival using tide tables (the Rule of Twelfths is useful for quick estimates). Check you have enough water under your keel at all stages — departure, any shallow patches en route, and arrival. Factor in your boat's draft plus a safety margin (typically 0.5m minimum).
Tidal Streams
Which way is the water flowing, and how fast? A 2-knot tidal stream against you at 5 knots boat speed means you're only making 3 knots over the ground. The same stream behind you means 7 knots. Use tidal stream atlases or Savvy Navvy to time your departure for a fair tide.
Springs vs Neaps
Spring tides (around new and full moon) have bigger ranges and stronger streams. Neap tides (quarter moons) are gentler. For challenging passages with strong tidal gates — like the Alderney Race, the Swinge, or the Strait of Messina — timing around neaps can make the passage dramatically safer and more comfortable.
Fuel & Range Calculation
Even on a sailing yacht, fuel planning matters. You need enough diesel for motoring in calms, charging batteries, and the possibility of motoring the entire passage if the wind dies.
The 30% Reserve Rule
Calculate the fuel you expect to use, then add 30%. This covers:
- Unexpected calms requiring more motoring than planned
- Adverse current increasing fuel consumption
- Diverting to a bolt hole (which may be further away)
- Higher consumption in rough weather
Quick Calculation
1. Distance to cover (nautical miles)
2. Expected motoring speed (knots) — typically 5-6 kts for a cruising yacht
3. Hours of motoring = Distance / Speed
4. Fuel consumption at cruising RPM (litres/hour) — check your engine manual
5. Total fuel = Hours x Consumption x 1.3 (30% reserve)
Crew Briefing
Before departure, brief your crew on the passage plan. Everyone on board should know:
The Route
Where are we going, which way, how long will it take? Show the route on the chart. Point out any waypoints where course changes happen.
Weather Expected
What wind are we expecting? From which direction? Is it forecast to change during the passage? What sea state?
Watch System
For passages over a few hours, establish a watch rota. Who is on watch when? Where should the off-watch crew rest? When are meals?
Emergency Procedures
Remind everyone of MOB procedure, life jacket locations, VHF operation, and fire extinguisher positions. If you have a safety brief, review it.
Bolt Holes
If things go wrong, where do we divert to? Make sure the crew knows there's always a Plan B — and that using it is good seamanship, not failure.
Passage Planning Checklist
Use this checklist before every passage. For short day sails, a quick mental run-through is enough. For longer passages, work through it properly.
Before Planning
- Charts available and up to date
- Pilot books / sailing directions consulted
- Notices to Mariners checked
- Tide tables available for departure and arrival ports
Route Planning
- Waypoints plotted with courses and distances
- Hazards identified with safe passing distances
- Bolt holes identified along the route
- ETAs calculated for each waypoint
Weather & Tides
- Weather forecast checked (multiple sources)
- Tidal heights calculated — enough depth everywhere
- Tidal streams checked — departure time optimised
- Abort criteria defined (max wind, sea state, visibility)
Vessel & Crew
- Fuel sufficient (with 30% reserve)
- Water and provisions adequate
- Safety equipment checked and accessible
- Crew briefed on plan, weather, watches, emergencies
- Shore contact informed of plan and ETA