Most of the questions a day on the water turns on are arithmetic you do not want to do standing on a dock: how much oil goes in this much petrol, how much thrust a loaded boat actually needs, what size that hook is, how long the battery will last at the speed you fish, and what the whole thing costs you in a season. These free tools answer one of those questions each, from your own numbers, in a few seconds. Nothing to sign up for, nothing to install, and they work on a phone with cold hands as well as on a laptop.
On-the-Water Calculators
Numbers in, an answer out: fuel mixes, thrust, run time, speed and what it all costs.
- 2-Stroke Fuel & Oil Mix CalculatorHow much oil goes in that much petrol, at any ratio, in ounces and millilitres.
- What a Boat Really CostsThe payment, then the year the banks’ calculators leave out.
- Trolling Motor & Battery CalculatorThrust, shaft length, volts and run time — for the boat as you actually load it.
Charts & Checklists
Reference you can tap on the dock, and lists that stop you forgetting the drain plug.
Where the numbers come from
Anything that touches safety is quoted from the body that sets it — the US Coast Guard’s own regulations, the ABYC standards, or the engine maker’s published specification — with the date it was last checked printed next to the answer. Where the boating world genuinely disagrees, and it often does, the tool shows both figures and says who says what instead of quietly picking one. Nothing here is invented, estimated to look precise, or averaged out of thin air.
Where a tool stops
A calculator is a starting point, not an authority. The capacity plate on your own boat outranks any number computed here. Your engine’s manual outranks any mix ratio. A required-equipment list is federal, and your state can add to it. And no tool can see the weather, the bottom you are anchoring in, or how tired you are — which is the part that usually decides how a day goes.
Share an answer, or keep it
Every result has its own link. Copy link saves exactly what you entered, so you can send a thrust figure to whoever is buying the motor, or open the fuel mix on your phone at the pump without typing it all again.
Put a tool on your own site
Every tool has an Embed button. It gives you a short piece of code to paste into a page, a forum post or a club website. The tool works there exactly as it does here, free, with a credit line linking back.
More from the site
The tools answer the quick questions. For the gear itself — kayaks, trolling motors, batteries, boats and tackle, used rather than unboxed — start with the latest posts.