Tools you might need next
Estimate cooling BTU load from room area and heat gain factors. Free online HVAC calculator with instant, accurate results.
Estimate heating BTU load from area and climate zone. Essential HVAC tool for planning, budgeting, and project optimization.
Size supply duct from airflow CFM and target velocity. Essential HVAC tool for planning, budgeting, and project optimization.
This tool applies a standard formula from the relevant domain. The computation is deterministic — given the same inputs, the result is always identical. The formula accounts for the primary variables that determine the output.
BTU from area × 25; Single zone: 9k–36k BTU; Multi-zone derate 10%The calculation requires: Zone Area, Number of Zones, Insulation. Each parameter contributes to the final result according to the formula above. Accuracy depends on the precision of your input measurements.
Updated: July 2026
A typical use case demonstrating the calculator with representative values.
→ Calculated result based on the formula and provided inputs
Enter your own values to get a personalized result for your specific situation.
→ Result calculated from your specific input values
Check the expected unit for each input field (shown as suffix). Converting between imperial and metric units before entering values prevents calculation errors.
When a formula combines multiple measurements, all inputs must use compatible units. Convert everything to the same system (metric or imperial) before calculating.
Size ductless mini-split system for room or zone cooling/heating. Free online HVAC calculator with instant, accurate results. It applies the calculation formula (BTU from area × 25; Single zone: 9k–36k BTU; Multi-zone derate 10%). For example: 500 sq ft single zone, good insulation — A typical use case demonstrating the calculator with representative values.