How this instrument works
A refrigeration ton is a rate of heat removal, not a mass, and the number that turns it into kilowatts is a fixed multiplier rather than a measured quantity: kW = tons × 3.5168525. The constant traces back to an American industry convention for rating compressors and chillers, but once that definition was locked in, the multiplication stopped needing any physical ice at all. It behaves exactly like converting inches to millimetres — no new physics happens inside the multiply, only a change of ruler. What actually changes is which industry reads the number naturally: the ton belongs to nameplates stamped in the United States, the kilowatt to nearly every electrical and mechanical spec sheet written anywhere else.
The eight-figure precision matters more than it looks. Round the factor to 3.5 and every ton is understated by about half a percent; that error is invisible on a single window unit but compounds fast across a commercial schedule with dozens of rooftop packages listed by tonnage. Because the multiplier is linear, a plant engineer can convert every nameplate separately and sum the kilowatts, or sum the tons first and convert once — both paths land on the same figure to the last decimal place, which is precisely the property a bid comparison or an equipment schedule depends on.
The one thing this multiplication cannot do is tell you what a machine actually delivers on site. A ton rating is measured under fixed test conditions set by an industry standard — a specific entering water or air temperature — and the kilowatt figure inherits that same assumption unchanged. Running the same compressor against a hotter outdoor coil or a lower chilled-water setpoint changes its real output well before any unit conversion enters the picture; this instrument converts the number printed on the label, not the performance the label implies under different weather.
- Enter the nameplate figure into Refrigeration tons — the tonnage stamped on a US-made compressor, chiller, or split-system spec sheet.
- Cooling power updates as you type; there is no separate calculate step to trigger.
- Switch Cooling power's unit menu between kW and W depending on which figure the target datasheet or tender document expects.
- For a building with several machines, convert each nameplate separately and add the kilowatt figures — the factor is linear, so the totals always agree.
Worked example — a 1-ton window unit's rating in kilowatts
A US-imported window air conditioner carries a nameplate rating of 1 ton, the standard US convention for small package and split units, and that figure needs translating before it means anything on a market that specifies chillers in kilowatts rather than tons. Multiply by the fixed factor: kW = 1 × 3.5168525 = 3.5168525 kW — equivalently 3,516.8525 W on the smaller scale a compact unit's label might use. The figure is exact to eight decimal places, so there is no rounding tolerance left to argue about on a purchase order.
The same multiplier scales without adjustment: a 5-ton commercial rooftop package, a common size for a small retail store, converts as kW = 5 × 3.5168525 = 17.5842625 kW, simply five times the single-ton figure. That linearity is what makes the conversion safe to apply across a whole mechanical schedule — add up the tons printed on every nameplate in a building, multiply the total once, and the kilowatt figure matches an engineer who converted each unit separately and summed them, down to the last decimal place.
Questions
Why is the factor 3.5168525 and not a rounder number like 3.5?
Because 3.5168525 is the exact value once a refrigeration ton is fixed at 12,000 BTU per hour and carried through the international BTU-to-joule definition; rounding to 3.5 understates every ton by roughly half a percent. That gap is invisible on one small unit but compounds into a real shortfall once a spec sheet lists dozens of machines, which is why this instrument keeps all eight figures.
Does this convert a ton of refrigeration or a ton of physical weight?
The ton of refrigeration — a rate of heat removal — never a ton of mass. The name borrows from an old ice-melting benchmark, but no kilogram or short ton of material enters this multiplication; the calculator only ever handles a cooling rate, in tons, and its equivalent in kilowatts.
Why do American nameplates use tons while most other countries use kilowatts?
It is industry convention, not physics. US refrigeration and HVAC manufacturing standardized on the ton before the kilowatt became the default power unit almost everywhere else, and equipment catalogues never switched over. Anyone comparing a US compressor against a European or Asian chiller has to cross the two conventions with exactly this multiplier, since both machines measure the same physical quantity.
Is the kilowatt figure the cooling a machine actually delivers on site?
Only under the same test conditions the ton rating was measured at — typically a fixed entering water or air temperature set by a standard such as AHRI. The 3.5168525 factor converts the rating number exactly; what changes with real weather or load is how much of that rated capacity the machine actually delivers, and this conversion neither captures nor corrects for that.
How do I go the other way, from kilowatts back to tons?
Divide the kilowatt figure by 3.5168525, the exact inverse of this multiplication. A 10 kW chiller, for example, rates at 10 ÷ 3.5168525 ≈ 2.84 tons — a figure worth keeping past the decimal point if it will be summed with other units before rounding to the nearest model a supplier actually stocks.
How is this different from converting BTU per hour to tons?
BTU/hr and tons are both American units for the same rate; this instrument instead bridges tons straight to the kilowatt, the SI unit almost every non-US spec sheet already carries. Starting from a BTU/hr figure rather than tons, divide by 12,000 first to reach tons, then apply this factor — or use a dedicated BTU-to-kilowatt instrument for that single step.