Standard F-150 tanks are often 23, 26, or 36 gallons.
Current percentage shown on your dashboard gauge.
The MPG from your trip computer (Running Average).
Fuel remaining when gauge hits "0 Miles to Empty". Typically 2-3 gal.
Estimated Distance To Empty0 Miles
Total Fuel Remaining:0.0 Gal
Usable Fuel (Before 0 DTE):0.0 Gal
Hidden Reserve Range:0 Miles
Understanding the Ford DTE Calculation
One of the most frequent questions from Ford owners—particularly those driving F-150s, Explorers, and Expeditions—concerns the accuracy and logic behind the "Distance To Empty" (DTE) display. Unlike a simple fuel gauge that measures volume, the DTE is a predictive algorithm that can fluctuate wildly based on driving conditions. This calculator allows you to reverse-engineer the math to understand your true range.
The Math Behind the "Miles to Empty" Display
The Ford DTE system calculates remaining range using two primary variables: the physical volume of fuel in the tank and the "Running Average Fuel Economy" (RAFE). The formula is generally represented as:
DTE = (Total Fuel – Reserve Buffer) × RAFE
For example, if you have a 36-gallon tank that is 50% full, and your truck has averaged 18 MPG over the last 500 miles, the math works as follows: 18 gallons total, minus a ~2-gallon hidden buffer (leaving 16 usable gallons), multiplied by 18 MPG equals a displayed DTE of 288 miles.
Why Does My DTE Drop Suddenly?
Owners often experience "DTE Shock" after towing a trailer or driving in the city. If you tow a boat for 100 miles, your fuel efficiency might drop from 20 MPG to 10 MPG. The Ford computer (the Intelligent Oil-Life Monitor and DTE system) updates its Running Average Fuel Economy (RAFE) based on this recent high consumption.
When you disconnect the trailer and fill up, the truck may still be calculating based on that 10 MPG history, resulting in a DTE reading that is drastically lower than expected (e.g., 300 miles instead of 600 miles). It usually takes 30-50 miles of normal driving for the RAFE to normalize.
The "Hidden" Reserve Buffer
Ford engineers design the DTE system to read "0 Miles to Empty" before the tank is physically dry. This is known as the reserve buffer. On most F-Series trucks, this buffer is approximately 2 to 3 gallons. This means that when your dashboard screams "0 Miles," you likely have roughly 30 to 50 miles of range left (depending on your MPG) before the engine actually stalls. Our calculator breaks this down specifically to show you the "Hidden Reserve Range."
Normal vs. Towing Mode
It is important to note that many modern Ford vehicles maintain two separate DTE history profiles:
Normal Mode: Uses a weighted average of the last ~500 miles of mixed driving.
Towing/Haul Mode: When a trailer is detected electrically, the system switches to a towing-specific fuel economy history to provide more conservative (and safer) range estimates.
function calculateFordDTE() {
// 1. Get input values strictly by ID
var tankCapacity = document.getElementById("tankCapacity").value;
var fuelGauge = document.getElementById("fuelGauge").value;
var avgMpg = document.getElementById("avgMpg").value;
var reserveBuffer = document.getElementById("reserveBuffer").value;
// 2. Validate inputs
if (tankCapacity === "" || fuelGauge === "" || avgMpg === "") {
alert("Please fill in Tank Capacity, Fuel Gauge Level, and MPG to calculate.");
return;
}
// 3. Parse floats
var capacityVal = parseFloat(tankCapacity);
var gaugeVal = parseFloat(fuelGauge);
var mpgVal = parseFloat(avgMpg);
var reserveVal = parseFloat(reserveBuffer);
// Handle default reserve if empty or invalid
if (isNaN(reserveVal)) {
reserveVal = 0;
}
// 4. Perform Calculation Logic
// Calculate total gallons currently in the tank
var currentGallons = capacityVal * (gaugeVal / 100);
// Calculate "Usable" gallons (what the computer sees before hitting 0 DTE)
var usableGallons = currentGallons – reserveVal;
// Edge case: If reserve eats up all fuel
if (usableGallons < 0) {
usableGallons = 0;
}
// Main DTE Calculation
var dteMiles = usableGallons * mpgVal;
// Calculate the range hidden in the reserve
// If current gallons is less than reserve, the hidden range is just what's left
var reserveRangeMiles = 0;
if (currentGallons < reserveVal) {
reserveRangeMiles = currentGallons * mpgVal;
} else {
reserveRangeMiles = reserveVal * mpgVal;
}
// 5. Update HTML Output
var resultBox = document.getElementById("resultBox");
resultBox.style.display = "block";
document.getElementById("dteResult").innerHTML = Math.round(dteMiles) + " Miles";
document.getElementById("fuelRemainingResult").innerHTML = currentGallons.toFixed(1) + " Gal";
document.getElementById("usableFuelResult").innerHTML = usableGallons.toFixed(1) + " Gal";
document.getElementById("reserveRangeResult").innerHTML = Math.round(reserveRangeMiles) + " Miles";
}