Specific heat calculator
Q = mcΔT, solved for whichever one you are missing. Water's value in that formula has an odd history: it is true by construction. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
Water's 4184 is a definition, not a measurement
The calorie was defined as the heat needed to raise one gram of water by one degree Celsius. So the statement "water has a specific heat of one calorie per gram per degree" is not a discovery about water. It is the definition of the calorie, read backwards.
That worked until people measured it carefully and found it was not constant — water takes slightly different amounts of heat per degree at different temperatures. A unit defined by a quantity that varies is not a unit, so the calorie was cut loose and fixed: the thermochemical calorie is exactly 4.184 joules, by agreement.
4184 J/(kg K) is that definition in SI units. The real specific heat of the water in front of you is near it and not exactly it, and the difference is a property of your water rather than of the number.
Water is strangely good at this
Water has an unusually high specific heat — it takes about ten times as much energy to warm a kilogram of water by a degree as it does a kilogram of copper. That is why the sea moderates coastal climates, why a hot water bottle works and a hot copper bottle would not, and why sweating is such an effective way to lose heat.
It is also why "it takes 4184 joules" feels like a big number for such a small change. It is a big number. That is the point of water.
ΔT is the same in Celsius and kelvin
A temperature change of one degree Celsius is a change of one kelvin exactly, because the two scales have the same size of degree and differ only in where zero sits. So ΔT needs no conversion, which is a rare kindness in a subject where getting the units wrong is usually the whole problem.
It is also a trap in the other direction: an absolute temperature must be in kelvin, a change may be in either, and the formula cannot tell which you handed it.