A fleet manager at a top-20 yacht management company recently spent 14 hours building a voyage budget for a single Palma-to-Athens crossing. Three spreadsheets. Three distance websites. Two phone calls to ports. He still missed the fuel cost by 22% because he used last month's bunker prices. The voyage went over budget. This is not an edge case — it is the normal way most yacht voyages are planned today.
Spreadsheets are free, flexible, and familiar. They are also slow, error-prone, and disconnected from the live data that determines whether a voyage budget holds up or falls apart. Here is an honest comparison — including where spreadsheets still win.
Where Spreadsheets Win
Let's be fair:
- Full customisation: Any formula, any layout, any report format
- No subscription cost: Google Sheets is free
- Offline access: Works without internet — important at sea
- Universal compatibility: Every accountant and owner can open one
If your operation is small, routes are predictable, and time is free, spreadsheets work. The problems start when scale, accuracy, and speed matter.
Where Spreadsheets Fail
1. Distance Calculations Are Wrong
Most spreadsheet plans use straight-line distances. The distance from Gibraltar to Cannes is 760nm in a straight line. The actual navigable route is closer to 810nm — a 6.5% difference. On a 50m yacht burning 25 L/nm, that 50nm error equals 1,250 litres of unplanned fuel, worth ~€1,400. SeaWise uses the Haversine formula with waypoint-based routing for 200+ ports.
2. Fuel Prices Are Always Out of Date
Bunker prices move 5-15% week to week. A spreadsheet captures a snapshot. SeaWise pulls live prices from Bunker Index, OilMonster, and LiveBunkers.
3. Speed vs. Fuel Is Simplified to the Point of Uselessness
Most spreadsheets use a single burn rate. But fuel consumption is a curve, not a line. At 10 knots your 50m yacht burns 180 L/hr. At 14 knots, 420 L/hr. A single-rate spreadsheet will underestimate fuel at high speeds by 30-40%.
4. Port Data Is Stale Before You Save
Port fees, marina availability, and clearance requirements change constantly. A spreadsheet with last year's Monaco berth fee (€300) will break your budget when the actual July cost is €1,200.
5. No Visual Route Verification
A spreadsheet gives you numbers. It does not show you the route. If your captain plans a route through a traffic separation scheme or restricted zone, a spreadsheet will not flag it. SeaWise displays the route on an interactive map.
6. Collaboration Is a Nightmare
"voyage_plan_FINAL.xlsx", "voyage_plan_FINAL_v2.xlsx", "voyage_plan_FINAL_v2_ACTUALLY_FINAL.xlsx". SeaWise stores data in the cloud. Captain, fleet manager, and owner see the same information in real time.
The Real Cost of Spreadsheet Errors
| Error Type | Frequency | Typical Impact |
|---|---|---|
| Wrong distance | Every voyage | 5-15% fuel budget error |
| Stale bunker prices | Every refuel | 5-15% fuel cost variance |
| Simplified burn rate | Every voyage | 10-20% fuel estimate error |
| Outdated port fees | Every port call | €200-1,000 per port |
| No route verification | Every voyage | Safety risk |
| Version control errors | Every collaboration | Hours of rework |
Over a 6-month season with 20+ voyages, these errors compound. A fleet manager using spreadsheets typically overshoots the annual voyage budget by 10-25%. For a fleet of three 50m yachts, that can mean €50,000-150,000 in unplanned costs.
Who Should Switch
Switch to SeaWise if: You plan more than 5 voyages per season, manage fuel budgets for multiple vessels, need to present accurate estimates to owners, or have experienced budget variance from spreadsheet planning.
Stick with spreadsheets if: You plan 1-2 voyages per year, your routes are always the same, or you have no budget accountability.
The Bottom Line
Spreadsheets were never designed for voyage planning. The maritime industry has used them for decades because there was no alternative. SeaWise does not replace your spreadsheet — it replaces the 4-6 hours you spend building one.