Boat Calculator: Marine Engine

Hull speed to anchor scope in seconds — pro marine calculators that work offshore with no signal needed. No ads, no subscription, one-time unlock.

Boat & Marine Engine Toolkit is a professional calculator suite for boat owners, marine engineers, naval architects, ship captains, and offshore platform crews. Run every calculation fully offline — at the dock, at anchor, or miles from the nearest cell tower. No ads, no accounts, no subscription.

From sizing ground tackle for a blow to checking prop shaft torque before sea trials, the toolkit puts trusted marine engineering formulas in your pocket and keeps them there.

WHAT'S INCLUDED: Fuel Burn & Range, Bollard Spacing, and the CG-719S reference are free. The other six calculators and five reference tables open with the one-time unlock below.

Navigation & Anchoring

• Hull Speed Calculator — compute theoretical hull speed and speed/length (S/L) ratio from waterline length for sailboats, trawlers, and displacement craft.
• Anchor Rode Scope — plan rode length from water depth, bow height, and tide for safe overnight holding.
• Concrete Anchor — allowable tension and shear for dock and pier fittings bolted into concrete, from anchor type, bolt diameter, embed depth, concrete f'c, and edge distance (ACI 318-19 Ch. 17).

Propulsion & Drivetrain

• Prop Shaft Torque — calculate shaft torque from engine horsepower and shaft RPM for gearbox and coupling sizing.
• Hydraulic Cylinder Force — push and pull force from bore, rod diameter, and system pressure for steering, hatch, and deck gear.
• Fuel Burn & Range — project burn rate in GPH, cruising range in nautical miles, and fuel cost per hour from engine power, engine load, tank capacity, and cruise speed in knots.

Safety & Compliance

• Bilge Pump Sizer — size pump capacity against hull volume with ABYC-aware guidance for peace of mind.
• Bollard Spacing — lay out vehicle-barrier bollards to ASTM F2656 K4/K8/K12: bollard count, maximum on-center spacing, and impact energy and force from vehicle weight, speed, and protected width.

Reference Tables

• Beaufort wind scale, anchor type comparison, ABYC bilge pump standards, shaft material properties, hydraulic cylinder sizes, and CG-719S return reasons — the numbers you actually reach for on deck.

WHO IS IT FOR:

• Boat owners planning passages, provisioning, and ground tackle
• Marine engineers sizing drivetrains, hydraulics, and auxiliaries
• Naval architects sanity-checking hull displacement and S/L figures
• Ship captains and mates running quick bridge calculations
• Offshore platform crews and workboat operators on deck
• Marine surveyors documenting condition and compliance notes

WHY MARINE PROS LOVE IT:

• 100% offline — every calculator runs on-device, so you never lose a tool when you lose signal offshore.
• No ads and no tracking — clean, focused screens built for use at sea.
• No subscription — pay once, own it, use it on every trip.
• Instant results — type values, get answers, move on to the next job on the checklist.
• Professional formulas — ABYC-aware guidance, standard naval architecture equations, and clear unit handling (knots, feet, inches, psi, bar, gallons, HP).

ONE-TIME UNLOCK: Unlock All Calculators is a single $12.99 USD in-app purchase. It is a one-time, non-consumable unlock — not a subscription. One payment opens every Pro calculator and every reference table, forever, on your Apple ID. Prop pitch planning, shaft torque, bilge pump sizing, hydraulic cylinder force, Beaufort references — all in.

Stow it in your pocket, keep it on the bridge, or pin it to the engine room iPad. Boat & Marine Engine Toolkit is built to be the quick, quiet answer to the everyday marine engine and offshore questions that keep boats running and crews safe.