Navigation, seamanship and ownership planning
Boating Calculators
Use 30 calculators covering navigation, fuel, anchoring, clearances, sailing performance, onboard systems, docking equipment, maintenance planning, and ownership costs.
Boating planning family
Fuel, Range & Propulsion
Use measured vessel data to estimate trip fuel, reserve and range scenarios, compare observed sea-trial economy, budget fuel cost, and calculate conventional propeller slip.
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Boat Trip Fuel Burn & Reserve Calculator
Estimate propulsion and auxiliary fuel burn by leg, then add measured-burn uncertainty, an explicit reserve, unusable fuel, and departure-fuel shortfall checks.
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Boat Cruising Range & Endurance Calculator
Calculate arithmetic and planning endurance, cruising range, return radius, reserve fuel, and burn-rate sensitivity from measured vessel data.
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Boat Fuel Economy & Best Cruise Calculator
Compare entered sea-trial RPM, speed, and fuel-burn rows to find the best observed nautical-mile economy and cost per nautical mile.
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Boat Fuel Cost Per Trip & Season Calculator
Estimate trip and seasonal marine fuel cost from nautical distance or engine hours, measured burn, price, auxiliary fuel, and reserve purchases.
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Boat Propeller Slip & Theoretical Speed Calculator
Calculate propeller RPM, theoretical no-slip speed, observed slip, expected speed at a selected slip, and input-uncertainty range.
Boating planning family
Anchoring, Tides & Clearances
Plan entered anchor scope and swing geometry, keep under-keel and overhead datum chains explicit, and compare simplified tide-height interpolation scenarios.
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Boat Anchor Rode & Scope Calculator
Calculate total vertical anchoring depth, required rode, achieved scope, rode shortfall, chain/rope allocation, and simplified horizontal projection.
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Boat Anchorage Swing Radius Calculator
Estimate simplified rode projection, conservative swing radius and diameter, tide scenarios, and clearance to entered neighbours or obstructions.
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Boat Under-Keel Clearance Calculator
Calculate available water depth, dynamic required depth, raw under-keel clearance, margin-adjusted clearance, and required compatible tide height.
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Sailboat Air Draft & Bridge Clearance Calculator
Compare verified vessel air draft and allowances with published bridge clearance using an explicit water-level adjustment and safety margin.
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Boat Tide Height & Clearance Window Calculator
Interpolate between user-entered official adjacent tide events, compare sinusoidal and rule-of-twelfths scenarios, and estimate threshold windows.
Boating planning family
Sailing Performance & Yacht Ratios
Explore empirical hull-speed references, sail geometry, descriptive yacht ratios, apparent/true wind vectors, and entered VMG options.
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Sailboat Hull Speed Calculator
Calculate an editable empirical displacement hull-speed reference, speed-length ratio, actual/reference percentage, and travel-time scenarios.
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Sailboat Sail Area Calculator
Estimate mainsail, foretriangle, headsail, total upwind, and reefed sail areas from P, E, I, J, roach, and LP/J inputs.
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Sailboat Design Ratios Calculator
Calculate conventional SA/D, D/L, ballast ratio, capsize screening formula, and comfort ratio with metric/imperial normalization.
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Sailing Apparent & True Wind Calculator
Convert between apparent and true wind using explicit relative-from angles, boat course and speed, optional current, and east/north vectors.
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Sailing VMG & Tack/Gybe Comparison Calculator
Compare two to four entered sailing options by current-adjusted VMG, leg time, distance sailed, manoeuvre penalty, and negative-VMG warnings.
Boating planning family
Onboard Capacity, Stores & Systems
Compare entered documented capacity, freshwater and holding-tank duration, bilge flow, and daily electrical energy.
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Boat Load & Capacity Plate Check Calculator
Compare entered people and gear loads with user-entered documented person and weight limits without deriving legal capacity.
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Boat Freshwater Provisioning & Tank Duration Calculator
Estimate daily freshwater demand, watermaker contribution, departure requirement, duration, reserve, and shortage.
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Boat Holding Tank & Pump-Out Interval Calculator
Estimate holding-tank daily inflow, reserve and full dates, required capacity, and pump-out timing.
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Boat Bilge Pump-Out Time Calculator
Compare rated and effective bilge flow, ongoing inflow, net removal, runtime, and remaining water.
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Boat Electrical Daily Energy Balance Calculator
Calculate daily marine electrical loads, critical demand, charging contribution, net balance, autonomy, and shedding scenarios.
Boating planning family
Maintenance, Docking & Ownership
Estimate bottom-paint purchases, dock-line geometry, fender placement, maintenance schedules and budgets, and annual operating costs.
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Boat Bottom Paint Quantity & Cost Calculator
Estimate or override wetted hull area, calculate coating by coats and supplier coverage, round whole packages, and estimate purchase cost.
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Boat Dock Line Length & Layout Calculator
Calculate geometric and purchase dock-line lengths, whole-size rounding, total inventory, and shortfall from entered berth offsets.
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Boat Fender Quantity & Spacing Planner
Solve whole fender count or even spacing across an entered protected hull zone and calculate one- or two-side inventory.
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Boat Seasonal Maintenance Schedule & Budget Calculator
Compare calendar and engine-hour service intervals, flag due tasks, and estimate parts, labour, haul/storage, contingency, and monthly budget.
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Boat Operating Cost Per Hour & Nautical Mile Calculator
Separate annual cash, fixed, variable, finance, contingency, and depreciation costs and calculate usage-based cost metrics.
Planning aids—not navigation instructions
These calculators do not replace a competent skipper, proper lookout, current charts and publications, notices, official tides and currents, marine forecasts, navigation rules, vessel documentation, local requirements, or safe alternatives. Never treat a geometric route, ETA, course correction, gate overlap, or watch rota as permission to proceed.