Contingency fuel calculator
A 2,000-unit trip with 5% contingency adds 100 units, and a 300-unit final reserve brings the total to 2,400: trip fuel, the percentage on top and the fixed floor in one line. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Trip fuel
- 2,000
- Contingency percent
- 5
- Final reserve
- 300
- Contingency fuel
- 100
- Total contingency and reserve
- 400
- Total fuel required
- 2,400
- Trip fuel source
- trip_fuel
Flight and long-trip fuel plans almost always add contingency on top of trip burn, then a fixed final reserve so the vehicle or aircraft is not planned down to empty tanks. Dispatchers, student pilots, and travel operators need a transparent number for contingency fuel as a percentage of trip fuel plus that fixed final reserve—without a full flight-management suite. This contingency fuel calculator accepts planned trip fuel (or trip burn rate times flight time in hours), a contingency percentage, and a fixed final reserve volume, then returns contingency fuel, total contingency-plus-reserve, and total fuel required.
Two layers of fuel on top of the trip
A fuel plan rarely stops at the fuel the trip itself should burn. Dispatchers, student pilots and travel operators add contingency fuel to cover what the forecast cannot promise: a change in wind, a routing delay, holding before landing or a burn higher than expected. In many training and operational templates it is a few percent of planned trip fuel. Below that sits the final reserve, a fixed amount set by company policy or a regulatory minimum, so the plan never counts down to empty tanks.
How the total is built, and the usual mistakes
The calculator multiplies trip fuel by the contingency percentage divided by one hundred, adds the fixed final reserve, and then adds trip fuel to give the total required. With 2,000 units of trip fuel and 5% contingency, that is 100 units plus a 300-unit reserve, or 2,400 in all. Common errors are treating the reserve as a second percentage, mixing kilograms with litres, and expecting the tool to apply regulatory tables, alternate airports or weather, which it does not. A zero trip fuel or a negative percentage is rejected.
How contingency fuel and final reserve are computed from trip fuel
Contingency fuel covers unplanned deviations: wind changes, routing delays, holding, or higher-than-forecast burn. In many training and operational templates it is expressed as a percentage of planned trip fuel—commonly a few percent—so a two-thousand-unit trip with five percent contingency adds one hundred units of contingency fuel. Final reserve is different: it is a fixed quantity held until the end of the plan (for example a regulatory minimum holding equivalent expressed as a fixed volume, or a company policy floor), not a second percentage of trip fuel.
Units are caller-chosen—kilograms, pounds, litres, or gallons—as long as trip fuel, contingency volume, and final reserve share the same unit.
What you can do with it
Dispatch and ops fuel planning
Operations tools apply company contingency percentages and fixed final reserve floors to planned trip burn for deterministic total fuel lines.
Burn-rate times flight-time planning
When only average burn and planned hours are known, derive trip fuel first, then add percentage contingency and fixed final reserve in one call.
FAQ
How does the contingency fuel calculator work?
Trip fuel can be supplied or derived from burn rate × flight time.
Is the contingency fuel calculator free?
The browser tool runs free on your device.
What is the difference between contingency fuel and final reserve?
Contingency fuel is a percentage of trip fuel that covers unplanned changes. Final reserve is a fixed quantity held until the end of the plan, such as a company or regulatory floor, and it is never a second percentage.
Can I work out trip fuel from burn rate and flight time?
Yes. Enter the average burn per hour and the planned flight time in hours instead of trip fuel. Their product becomes trip fuel, and the contingency percentage and final reserve are then added in the same step.
Which units can I use for the fuel?
Kilograms, pounds, litres or gallons all work, as long as trip fuel, burn rate and final reserve share the same unit. The calculator never converts mass into volume, so mixing kilograms with litres gives a wrong total.
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/contingency-fuel \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"trip_fuel":2000,"contingency_percent":5,"final_reserve":300}'const res = await fetch("https://api.kit.forhosting.com/travel/contingency-fuel", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"trip_fuel": 2000,
"contingency_percent": 5,
"final_reserve": 300
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/travel/contingency-fuel",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"trip_fuel": 2000,
"contingency_percent": 5,
"final_reserve": 300
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/travel/contingency-fuel", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"trip_fuel":2000,"contingency_percent":5,"final_reserve":300}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"trip_fuel":2000,"contingency_percent":5,"final_reserve":300}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/travel/contingency-fuel", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"trip_fuel": 2000,
"contingency_percent": 5,
"final_reserve": 300
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "travel.contingency_fuel",
"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.
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
The same pure arithmetic runs free in the browser and at $0.002 per successful API item, so training worksheets, dispatch tools, and automation pipelines stay byte-for-byte consistent.
How contingency fuel and final reserve are computed from trip fuel
This calculator multiplies trip fuel by contingency percent over one hundred to obtain contingency_fuel, then adds the caller-supplied final_reserve to form total_contingency_and_reserve, and finally adds trip fuel to produce total_fuel_required. Trip fuel may be entered directly when you already know the route burn, or derived when you supply trip_burn_rate and flight_time_hours: the product of rate and hours becomes trip_fuel with trip_fuel_source set to burn_rate_times_flight_time. The endpoint does not look up regulatory tables, alternate airports, or weather; it only applies the percentage-plus-fixed-reserve identity so results stay deterministic and auditable. Zero trip fuel, negative percentages, or missing required fields fail with invalid_input rather than inventing a default policy percentage.
Input contract, response fields, units, and error behaviour
Keep units coherent yourself; this tool never converts mass to volume or hours to minutes. POST a JSON body with required contingency_percent (non-negative finite percentage of trip fuel; aliases contingency_pct, percent, contingency, contingency_percentage, pct) and final_reserve (non-negative fixed reserve in the trip fuel unit; aliases reserve, final_reserve_fuel, fixed_reserve, reserve_fuel, final_res). Supply trip fuel either as trip_fuel (strictly positive; aliases trip, fuel_trip, trip_fuel_volume, planned_trip_fuel) or as both trip_burn_rate and flight_time_hours (each strictly positive; burn aliases burn_rate, fuel_flow, trip_flow, consumption_rate, burn; time aliases flight_time, hours, trip_time, duration_hours, block_time_hours). When trip_fuel is present it is used even if burn and time are also sent; optional burn and time are then echoed for documentation. Numeric fields may be JSON numbers or numeric strings. Missing trip source, non-positive trip fuel or burn or time, negative contingency or reserve, empty strings, NaN, and Infinity all fail with invalid_input and are not billed. On success the body includes cleaned trip_fuel, contingency_percent, contingency_fuel, final_reserve, total_contingency_and_reserve, total_fuel_required, trip_fuel_source (trip_fuel or burn_rate_times_flight_time), formula, and method contingency_percent_plus_fixed_final_reserve. Optional trip_burn_rate and flight_time_hours appear only when provided or used. Example: trip_fuel two thousand, contingency_percent five, final_reserve three hundred yields contingency_fuel one hundred, total_contingency_and_reserve four hundred, and total_fuel_required two thousand four hundred.
API usage, pricing, flight-planning workflows, and practical limits
Use the free in-browser contingency fuel calculator for student worksheets, preflight sketches, and classroom demos of percentage contingency plus fixed final reserve without installing a spreadsheet. Source inputs follow the same retention rules as other KIT parse items, and results are safe to snapshot because the algorithm is fully deterministic with no network, random seed, or wall clock. Document the volume or mass unit you chose, keep requests small, and you get reproducible contingency fuel figures for dashboards, training apps, and edge workers without hosting custom fuel-policy arithmetic of your own. Use the prepaid API when a dispatch portal, FBO tool, travel ops dashboard, or LMS needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance. Pair this endpoint with separate trip fuel volume or fuel cost calculators when you need distance-based economy or currency totals; this capability answers only the contingency-and-final-reserve slice of the fuel plan. It does not model alternates, taxi, APU, or tankering economics.
Integration use cases
Flight training and preflight worksheets
Instructors and students enter trip fuel, contingency percent, and final reserve to see contingency fuel and total fuel required with the same math as the API.
Technical questions
What units should I use for trip fuel and final reserve?
Any coherent mass or volume unit—kg, lb, litres, gallons—as long as trip_fuel, contingency volume, and final_reserve use the same unit. The calculator does not convert units.
Can I compute trip fuel from burn rate and flight time?
Yes. Omit trip_fuel and send trip_burn_rate with flight_time_hours; trip_fuel becomes their product and trip_fuel_source is burn_rate_times_flight_time.
Does it apply ICAO or FAA regulatory tables automatically?
No. You choose contingency_percent and final_reserve to match your regulation, company policy, or training exercise. The endpoint only applies the percentage-plus-fixed-reserve arithmetic.