Enter any two known values (Voltage, Current, Resistance) to solve for the rest, including power.
Result
Fill in exactly two fields and leave the third blank to solve for it. If all three are filled, power is calculated directly. Formulas: V = I × R · P = V × I · P = I² × R · P = V² / R.
Voltage Drop Calculator
Estimate voltage drop across a cable run. Uses standard copper/aluminium resistivity constants (IEC-style, metric cable sizes).
Voltage Drop
Uses resistivity of 0.0175 Ω·mm²/m (copper) or 0.0282 Ω·mm²/m (aluminium) at ~20°C. Single-phase: Vd = (2 × L × I × ρ) / A. Three-phase: Vd = (√3 × L × I × ρ) / A. Most standards (e.g. IEC/BS 7671) recommend keeping voltage drop under 3-5% of supply voltage. This is a planning estimate — actual drop varies with conductor temperature and installation method.
Cable Sizing Reference (Copper, PVC-Insulated)
Approximate current-carrying capacity for common copper cable sizes, based on typical IEC 60364-5-52 reference method values. Always confirm against the specific installation method and apply correct derating.
Cross-Section (mm²)
Free Air / Clipped Direct (A)
Enclosed in Conduit (A)
1.5
~19.5 A
~14 A
2.5
~27 A
~18.5 A
4
~36 A
~25 A
6
~46 A
~32 A
10
~63 A
~43 A
16
~85 A
~57 A
25
~112 A
~75 A
35
~138 A
~92 A
50
~168 A
~110 A
70
~213 A
~139 A
95
~258 A
~167 A
Indicative values only, for quick reference — not a substitute for the full IEC 60364-5-52 tables. Actual permitted current depends on the specific reference installation method (A1, A2, B1, B2, C, etc.), ambient temperature, grouping with other circuits, and insulation type. Apply correction/derating factors for ambient temperature above 30°C and for cables grouped together. Always verify with the applicable local wiring regulations before final sizing.
Cooling Load (BTU) Quick Estimate
A rough sizing estimate for choosing an AC unit — not a substitute for a full room-by-room load calculation.
Estimated Cooling Capacity Needed
Rule-of-thumb estimate for a hot climate (UAE): base load of ~750 BTU/h per m², adjusted for sun exposure, occupancy (+600 BTU/h per person beyond 2), and kitchens (+4,000 BTU/h). Actual required capacity depends on insulation quality, window area and glazing type, ceiling height, and local peak design temperature. For commercial installations or critical spaces, use a full ASHRAE Manual J-style load calculation or consult one of our technicians.
Duct Sizing & CFM Calculator
Convert cooling capacity to required airflow, and airflow to round duct diameter at a target air velocity.
Required Round Duct Diameter
CFM from BTU/h uses the common approximation: CFM = BTU/h ÷ (1.08 × 20°F design temperature split) — a standard rule-of-thumb assuming a 20°F supply-to-return temperature differential. Duct diameter is derived from CFM and target velocity assuming a round duct (Area = CFM ÷ Velocity; Diameter from Area). Typical supply duct velocities range 600-900 ft/min for residential, higher for commercial trunk lines — verify against ASHRAE/SMACNA guidance for the specific application.
Superheat & Subcooling Calculator
Read the saturation temperature off your gauge's built-in P-T chart (or a digital manifold) for the measured pressure, then enter it here alongside your measured line temperature.
Result
Superheat = Measured Suction Line Temp − Saturation Temp at suction pressure. Subcooling = Saturation Temp at liquid pressure − Measured Liquid Line Temp. Typical target ranges (verify against the specific unit's manufacturer spec, which always takes precedence): fixed-orifice systems often target ~10-20°F (~5.5-11°C) superheat; TXV systems often target ~8-12°F (~4.5-6.5°C) superheat; subcooling is commonly targeted around 10-15°F (~5.5-8.5°C) but varies significantly by manufacturer and system design. We deliberately do not embed a refrigerant pressure-to-temperature lookup table here, since P-T values differ by refrigerant (R410A, R22, R32, R134A, etc.) and accuracy matters — use your gauge's own chart or app for that conversion.
