function calculateRate() {
// Clear errors
var errorDiv = document.getElementById('errorDisplay');
errorDiv.style.display = 'none';
errorDiv.innerHTML = ";
// Get inputs
var rentAmount = parseFloat(document.getElementById('totalRent').value);
var frequency = document.getElementById('rentFrequency').value;
var sqft = parseFloat(document.getElementById('squareFootage').value);
var addCosts = parseFloat(document.getElementById('additionalCosts').value);
// Validation
if (isNaN(rentAmount) || rentAmount <= 0) {
errorDiv.innerHTML = "Please enter a valid rent amount.";
errorDiv.style.display = 'block';
return;
}
if (isNaN(sqft) || sqft <= 0) {
errorDiv.innerHTML = "Please enter a valid square footage.";
errorDiv.style.display = 'block';
return;
}
if (isNaN(addCosts)) {
addCosts = 0;
}
// Calculations
var annualBaseRent = 0;
var monthlyBaseRent = 0;
if (frequency === 'monthly') {
monthlyBaseRent = rentAmount;
annualBaseRent = rentAmount * 12;
} else {
annualBaseRent = rentAmount;
monthlyBaseRent = rentAmount / 12;
}
var annualBaseRatePerSqFt = annualBaseRent / sqft;
var monthlyBaseRatePerSqFt = monthlyBaseRent / sqft;
// Gross Calculations (Including Additional Costs)
// Additional costs are assumed to be Monthly in the input label
var annualAddCosts = addCosts * 12;
var totalAnnualGrossRent = annualBaseRent + annualAddCosts;
var grossRatePerSqFtAnnual = totalAnnualGrossRent / sqft;
// Display Results
document.getElementById('resultContainer').style.display = 'block';
// Formatting function
function formatMoney(num) {
return '$' + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
document.getElementById('resAnnualRate').innerHTML = formatMoney(annualBaseRatePerSqFt) + " / sq ft / yr";
document.getElementById('resMonthlyRate').innerHTML = formatMoney(monthlyBaseRatePerSqFt) + " / sq ft / mo";
document.getElementById('resTotalAnnual').innerHTML = formatMoney(annualBaseRent);
document.getElementById('resGrossRateAnnual').innerHTML = formatMoney(grossRatePerSqFtAnnual) + " / sq ft / yr";
}
How to Calculate Rental Rate Per Square Foot
Calculating the rental rate per square foot is a fundamental skill in real estate analysis, whether you are leasing commercial office space, renting a retail storefront, or evaluating residential property investments. It allows tenants and landlords to compare properties of different sizes on an equal footing.
The Basic Formula
The calculation differs slightly depending on whether you are looking for an annual rate (common in commercial real estate) or a monthly rate (common in residential real estate).
Annual Rate Formula:
(Monthly Rent × 12) ÷ Total Square Footage = Annual Rate per Sq Ft
Monthly Rate Formula:
Monthly Rent ÷ Total Square Footage = Monthly Rate per Sq Ft
Step-by-Step Calculation Guide
Determine Total Rent: Identify the total base rent amount. If the rent is quoted monthly, multiply by 12 to get the annual figure for commercial comparisons.
Determine Square Footage: Locate the total rentable square footage of the property. In commercial leases, clarify if this is "Useable Square Footage" or "Rentable Square Footage" (which includes shared common areas).
Divide Price by Area: Take the total rent and divide it by the square footage.
Commercial vs. Residential Quotes
One common point of confusion is how rates are quoted:
Commercial (Office/Retail/Industrial): Typically quoted as an annual price per square foot. If a landlord says the rate is "$25.00/sq ft", they usually mean you pay $25.00 per square foot per year.
Residential (Apartments/Homes): Typically quoted as a monthly price per square foot in analytical contexts, though listings usually show the total monthly rent price.
Gross vs. Net Rental Rates
When calculating rental rates, it is crucial to understand what is included in the cost:
Full Service / Gross Lease: The rate per square foot includes base rent plus operating expenses like utilities, taxes, and maintenance.
Triple Net (NNN): The rate per square foot quoted is only the base rent. Tenants must pay property taxes, insurance, and maintenance separately (CAM charges).
Use the calculator above to input "Additional Monthly Costs" to see how extra fees like NNN charges or HOA fees impact your effective rental rate per square foot.
Example Calculation
Imagine you are looking at a 2,000 sq ft office space with a monthly rent of $4,000.
To find the Annual Rate:
1. Annual Rent = $4,000 × 12 = $48,000
2. Rate = $48,000 ÷ 2,000 sq ft = $24.00 per sq ft / yr
To find the Monthly Rate:
Rate = $4,000 ÷ 2,000 sq ft = $2.00 per sq ft / mo