Aircraft Rate of Climb Calculator
.roc-calculator-container {
max-width: 600px;
margin: 0 auto;
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 25px;
background-color: #f9fbfd;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.roc-header {
text-align: center;
margin-bottom: 25px;
color: #2c3e50;
}
.roc-header h2 {
margin: 0;
font-size: 24px;
}
.roc-mode-selector {
display: flex;
justify-content: center;
gap: 20px;
margin-bottom: 20px;
padding-bottom: 15px;
border-bottom: 1px solid #ddd;
}
.roc-label-radio {
cursor: pointer;
font-weight: 600;
color: #555;
display: flex;
align-items: center;
gap: 5px;
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
color: #444;
}
.input-group input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.input-group .unit {
font-size: 0.85em;
color: #777;
margin-left: 5px;
}
.roc-btn {
width: 100%;
padding: 12px;
background-color: #0056b3;
color: white;
border: none;
border-radius: 4px;
font-size: 16px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.3s;
}
.roc-btn:hover {
background-color: #004494;
}
.roc-result {
margin-top: 20px;
padding: 15px;
background-color: #e8f4fc;
border-left: 5px solid #0056b3;
border-radius: 4px;
display: none;
}
.roc-result h3 {
margin-top: 0;
color: #0056b3;
font-size: 18px;
}
.roc-result-value {
font-size: 28px;
font-weight: bold;
color: #333;
}
.roc-explanation {
margin-top: 40px;
font-family: inherit;
line-height: 1.6;
color: #333;
}
.roc-explanation h2 {
color: #2c3e50;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
}
.roc-explanation h3 {
color: #0056b3;
margin-top: 25px;
}
.roc-explanation ul {
padding-left: 20px;
}
.hidden-section {
display: none;
}
Altitude Over Time
Departure Gradient
Calculate Rate of Climb
Calculated Vertical Speed
0 fpm
How to Calculate Rate of Climb (ROC) for an Aircraft
Rate of Climb (ROC) is a critical performance metric in aviation, representing the vertical speed of an aircraft—specifically, how much altitude is gained over a specific unit of time. It is typically measured in feet per minute (fpm) . Pilots use this calculation to verify aircraft performance against the Operating Handbook (POH) or to ensure compliance with Instrument Departure Procedures (SIDs) and obstacle clearance requirements.
Formula 1: Altitude Change Over Time
This is the most basic method used to determine the average rate of climb during a flight leg. It is useful for verifying actual aircraft performance.
Formula: ROC = (Target Altitude - Starting Altitude) / Time in Minutes
Example:
Altitude Change: 4,500 – 1,000 = 3,500 ft
Time: 7 minutes
Calculation: 3,500 / 7 = 500 fpm
Formula 2: Departure Gradient (IFR Requirements)
During instrument departures, procedures often specify a minimum climb gradient in feet per Nautical Mile (ft/NM) rather than feet per minute. To convert this to a vertical speed on your Variometer (VSI), you must account for your ground speed.
Formula: ROC = (Ground Speed (knots) × Climb Gradient (ft/NM)) / 60
Example: 300 ft/NM to clear an obstacle. Your aircraft climbs at a ground speed of 120 knots .
Ground Speed: 120 kts (approx 2 NM per minute)
Calculation: (120 × 300) / 60 = 600 fpm
This means you must maintain at least 600 fpm on your Vertical Speed Indicator to satisfy the gradient requirement at that specific ground speed.
Factors Affecting Rate of Climb
Real-world ROC is influenced by several aerodynamic and environmental factors:
Power Setting: Excess power (Power Available – Power Required) determines climb performance.Weight: Heavier aircraft require more lift and have less excess power available for climbing.Density Altitude: Higher temperatures and altitudes reduce engine performance and propeller efficiency, decreasing ROC.Configuration: Flaps and landing gear increase drag, significantly reducing the rate of climb.
function toggleMode() {
var radios = document.getElementsByName('calcMode');
var timeInputs = document.getElementById('timeInputs');
var gradientInputs = document.getElementById('gradientInputs');
var resultDiv = document.getElementById('resultOutput');
// Hide result when switching modes
resultDiv.style.display = 'none';
for (var i = 0; i < radios.length; i++) {
if (radios[i].checked) {
if (radios[i].value === 'time') {
timeInputs.style.display = 'block';
gradientInputs.style.display = 'none';
} else {
timeInputs.style.display = 'none';
gradientInputs.style.display = 'block';
}
}
}
}
function calculateRateOfClimb() {
var radios = document.getElementsByName('calcMode');
var mode = 'time';
for (var i = 0; i < radios.length; i++) {
if (radios[i].checked) {
mode = radios[i].value;
break;
}
}
var roc = 0;
var details = "";
var resultDiv = document.getElementById('resultOutput');
var resultValue = document.getElementById('resultValue');
var resultDetails = document.getElementById('resultDetails');
if (mode === 'time') {
var start = parseFloat(document.getElementById('startAlt').value);
var end = parseFloat(document.getElementById('endAlt').value);
var time = parseFloat(document.getElementById('timeElapsed').value);
if (isNaN(start) || isNaN(end) || isNaN(time) || time <= 0) {
alert("Please enter valid numerical values. Time must be greater than zero.");
return;
}
var altitudeChange = end – start;
roc = altitudeChange / time;
details = "Total Gain: " + altitudeChange.toLocaleString() + " ft over " + time + " minutes.";
// Handle descent
if (roc < 0) {
resultValue.style.color = "#d9534f"; // Red for descent
details = "Total Loss: " + Math.abs(altitudeChange).toLocaleString() + " ft over " + time + " minutes.";
} else {
resultValue.style.color = "#333";
}
} else {
var gs = parseFloat(document.getElementById('groundSpeed').value);
var gradient = parseFloat(document.getElementById('climbGradient').value);
if (isNaN(gs) || isNaN(gradient) || gs < 0 || gradient < 0) {
alert("Please enter valid positive numbers for Speed and Gradient.");
return;
}
// Formula: (GS * Gradient) / 60
// Logic: GS is NM/hr. Gradient is ft/NM.
// Result is ft/hr. Divide by 60 for ft/min.
roc = (gs * gradient) / 60;
details = "At " + gs + " kts, you cover " + (gs/60).toFixed(2) + " NM per minute.";
resultValue.style.color = "#333";
}
resultValue.innerHTML = Math.round(roc).toLocaleString() + " fpm";
resultDetails.innerHTML = details;
resultDiv.style.display = 'block';
}