Boat fuel consumption calculator
A 90-nautical-mile run at 18 knots takes five hours, so engines burning 12.5 litres an hour use 62.5 litres, also shown as 16.511 US gallons and 13.748 imperial gallons. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Fuel burn rate
- 12.5
- Cruising speed
- 18
- Distance
- 90
- Fuel burn unit
- Liters per hour
- Precision
- 3
- Voyage hours
- 5
- Fuel used
- 62.5
- Fuel unit
- liters
- Fuel used liters
- 62.5
This boat fuel consumption calculator estimates how much fuel a voyage will use when you know the route distance in nautical miles, the boat's planned cruising speed in knots, and the engine's hourly fuel-burn rate. It first calculates underway time, then multiplies those hours by the stated burn rate. Results appear in the selected fuel unit as well as liters, US gallons, and imperial gallons, making the estimate useful for trip planning, quotation work, and comparing figures from different manuals or fuel docks.
Gather a realistic cruising burn rate
Start with the combined hourly burn rate for every propulsion engine that will run during the passage. The best figure comes from a fuel-flow meter or a recent log entry recorded at the same revolutions per minute, load, trim, and typical sea state you plan to use. Manufacturer performance tables are a useful second choice, but their test boat may be lighter, cleaner, and more carefully trimmed than yours.
If a twin-engine boat burns 6 US gallons per hour on each engine, enter 12 rather than 6. Choose the matching unit instead of converting it yourself. The calculator accepts liters per hour, US gallons per hour, or imperial gallons per hour and reports equivalent totals in all three volume systems.
Avoid using a maximum-throttle specification when you intend to cruise economically, and avoid an idle figure for a voyage made mostly on plane. An honest input matters more than extra decimal places because the calculation assumes that one burn rate represents the whole underway period. Auxiliary generator, cabin heater, and tender fuel are not automatically included; add their expected consumption separately if they share the voyage fuel supply.
Calculate underway time from nautical miles and knots
Enter route distance in nautical miles and cruising speed in knots. A knot is one nautical mile per hour, so voyage hours equal distance divided by speed without another unit conversion. For example, a 90-nautical-mile passage at 18 knots takes five underway hours in steady conditions.
Use the distance of the route you expect to steer, not merely a straight line between departure and arrival. Channels, traffic-separation schemes, restricted water, headlands, and planned detours can make the navigable route longer. Likewise, cruising speed should represent speed made good over the route.
Strong current, wind, waves, fouling, and time spent maneuvering can reduce the average even if the speed display often shows the target number. The returned voyage time is a mathematical underway estimate, not an arrival forecast: it excludes stops unless their distance-equivalent effect is already reflected in your average speed. If the distance is zero, the calculator returns zero hours and zero fuel; speed and burn rate must still be positive because they define a valid operating scenario.
Use the precision control only to format results, not to imply that real marine conditions are equally exact.
Turn the estimate into a safe fuel plan
The core formula is fuel used equals distance divided by cruising speed, multiplied by fuel burn per hour. Treat that result as the estimated consumption for the stated conditions, not the amount that should be loaded aboard. A practical passage plan normally adds fuel for startup, warm-up, harbor maneuvering, weather or current delays, diversions, generator use, and a reserve appropriate to the vessel, route, regulations, and operator's safety policy.
This calculator deliberately does not choose a reserve percentage because suitable margins differ greatly between a short protected-water trip and an offshore passage with few alternates. Check the estimated total against usable tank capacity rather than the tank's nominal size; inaccessible fuel, gauge error, contamination, and vessel trim can reduce what the engines can actually draw. For planning repeated trips, compare predicted consumption with fuel added and reliable flow-meter or tank records, then update the burn-rate assumption.
If actual use is consistently higher, investigate loading, hull or propeller fouling, engine condition, trim, sea state, and routing.
What you can do with it
Plan a coastal passage
Estimate underway hours and propulsion fuel before adding the skipper's chosen contingency and reserve.
Compare cruise settings
Run measured speed and burn-rate pairs to see which operating point is likely to use less fuel over the same route.
Prepare a charter estimate
Convert route distance and the vessel's documented hourly burn into a consistent voyage fuel allowance for a quotation.
FAQ
What formula does the calculator use?
Voyage hours equal nautical miles divided by knots. Fuel used equals voyage hours multiplied by the hourly fuel-burn rate.
Should I enter the burn rate for one engine or all engines?
Enter the combined hourly rate for all propulsion engines expected to run. Add other fuel-consuming equipment separately if needed.
Does the result include a fuel reserve?
No. It estimates consumption under the entered conditions. Add a reserve and operational allowances suitable for your vessel and passage.
Which gallon does the calculator use?
Select US gallons per hour or imperial gallons per hour explicitly. The result also provides conversions to liters and both gallon definitions.
Why might actual fuel use be higher?
Wind, waves, adverse current, fouling, load, trim, maneuvering, engine condition, detours, and auxiliary equipment can all raise real consumption.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/travel/boat-fuel-consumption \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"fuel_burn_rate":12.5,"cruising_speed":18,"distance":90}'const res = await fetch("https://api.kit.forhosting.com/travel/boat-fuel-consumption", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"fuel_burn_rate": 12.5,
"cruising_speed": 18,
"distance": 90
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/travel/boat-fuel-consumption",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"fuel_burn_rate": 12.5,
"cruising_speed": 18,
"distance": 90
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/travel/boat-fuel-consumption", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"fuel_burn_rate":12.5,"cruising_speed":18,"distance":90}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"fuel_burn_rate":12.5,"cruising_speed":18,"distance":90}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/travel/boat-fuel-consumption", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"fuel_burn_rate": 12.5,
"cruising_speed": 18,
"distance": 90
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "travel.boat_fuel_consumption",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_input | 1000000000 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Turn the estimate into a safe fuel plan
The API price is $0.002 per calculation, while the page can run the same deterministic arithmetic locally for quick checks.
Technical questions
What does an API calculation cost?
Each API calculation costs $0.002. The on-page calculator can run the same deterministic formula in the browser.