How many calories are in 1 BTU?

1 BTU (International Table) = 252.1644 thermochemical calories (small cal). In food terms, this is about 0.252164 kilocalories.

What’s the difference between cal and kcal?

The small calorie (cal) is the amount of energy needed to raise 1 g of water by 1°C. The kilocalorie (kcal), often just called 'Calorie' in nutrition labels, is 1000 small calories. Our tool converts to both.

Why are there different BTU and calorie definitions?

Because BTU and calorie were historically defined using slightly different reference temperatures. Engineering and nutrition sources may use different variants. This calculator lets you pick the exact combination.

BTU to Calories Converter (BTU ⇄ cal ⇄ kcal)

How to use this converter

The calculator handles BTU and calorie conversions by normalizing every input through joules. Switch modes to either convert BTUs to calories or reverse the flow from calories to BTUs, and choose the definition that matches your data source.

Adjust each unit definition dropdown to reflect whether your source uses the International Table (IT), thermochemical, mean, or food kilocalorie standards. Both conversions remain synchronized with the same rounding and precision from the legacy page.

BTU (IT)	kcal (food)	cal (th)
1	0	0
2	0	0
5	0	0
10	0	0

Mode guidance

Use the calculator button for immediate recomputation after changing a toggle, and rely on the 100 ms debounce when typing to keep the UI responsive yet stable.

Reset returns every value and dropdown to the documented defaults so you can reproduce the canonical examples or start from scratch.

Full original guide (expanded)

Conversion formulas

General method: convert everything through joules (J).

BTU → J: J = BTU × BTU_factor

J → cal: cal = J ÷ cal_factor

BTU → cal: cal = BTU × BTU_factor ÷ cal_factor

Example: 1 BTU (IT) × 1055.05585262 ÷ 4.184 = 252.1644 cal

When to pick which unit

BTU (IT): most common in HVAC, US engineering tables.
BTU (thermochemical): used in some older thermodynamics literature.
cal (thermochemical): standard for scientific conversion (4.184 J).
kcal: food labels, nutrition, “Calories” with capital C.

FAQ

1. Why do different sites show slightly different results?

They may be mixing BTU (IT) and BTU (thermochemical), or using 4.1868 J per calorie instead of 4.184 J. Our calculator shows you the exact factors used.

2. Are “nutrition calories” the same as kilocalories?

Yes. 1 kcal = 1 Cal (with capital C) = 1000 small calories.

3. Can I go from m³ gas → BTU → calories?

Yes, but you first need the energy content of the gas in BTU or MJ. This page handles the BTU ↔ calorie part.

Related energy converters

Engineering notes

State your BTU definition in reports.
Round to 3–4 decimals for invoices.
For HVAC loads, BTU (IT) is the safest assumption.

BTU to Calories Converter

Energy conversion controls

BTU → calories

calories → BTU