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Foot-pounds to Btus (th) Converter (ft·lb to Btu (th))

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Live Conversion • ISO 80000-5:2019 Certified
1 Foot-pound = 0.0012859275 Btu (th)
1 ft·lb = 0.00128593 Btu (th) • 1 Btu (th) = 777.648847 ft·lb
Foot-pound to Btu (th): One Foot-pound is equal to 0.0012859275 Btus (th).
Certified Authority Value
0.00128593
Btu (th)
Exact: 1 Btu (th) ≡ 777.6488471675 ft·lb
ft·lb
ft·lb
Swap to Btu (th) to Foot-pound
Swap to Btu (th) to Foot-pound
Btu (th)
Btu (th) 0.0012859275
Quick Values:
Conversion Formula
To convert Foot-pound to Btu (th), multiply by 0.0012859275
ft·lb × 0.0012859275 = Btu (th)

Calculation: 1 ft·lb × 0.0012859275 = 0.0012859275 Btu (th)

Common Foot-pound to Btu (th) Calculations

Quick-lookup reference table showing calculated equivalents for standard increments between Foot-pound (ft·lb) and Btu (th) (Btu (th)).

Tap any row to calculate
Foot-pound to Btu (th): Primary Direct Table (15 Steps)
Foot-pound to Btu (th) Conversion Reference Table
Conversion & Equivalent Value Scientific Notation
0.001 ft·lb 1.285927 × 10⁻⁶ Btu (th) 1.286 × 10⁻⁶
0.01 ft·lb 1.285927 × 10⁻⁵ Btu (th) 1.286 × 10⁻⁵
0.1 ft·lb 0.000128593 Btu (th) 1.286 × 10⁻⁴
0.5 ft·lb 0.000642964 Btu (th) 6.43 × 10⁻⁴
1 ft·lb 0.00128593 Btu (th) 1.286 × 10⁻³
2 ft·lb 0.00257185 Btu (th) 2.572 × 10⁻³
5 ft·lb 0.00642964 Btu (th) 6.43 × 10⁻³
10 ft·lb 0.0128593 Btu (th) 1.286 × 10⁻²
20 ft·lb 0.0257185 Btu (th) 2.572 × 10⁻²
25 ft·lb 0.0321482 Btu (th) 3.215 × 10⁻²
50 ft·lb 0.0642964 Btu (th) 6.43 × 10⁻²
100 ft·lb 0.128593 Btu (th) 1.286 × 10⁻¹
250 ft·lb 0.321482 Btu (th) 3.215 × 10⁻¹
500 ft·lb 0.642964 Btu (th) 6.43 × 10⁻¹
1000 ft·lb 1.285927 Btu (th) 1.286 × 10⁰
Btu (th) to Foot-pound: Reciprocal Summary
Btu (th) to Foot-pound Conversion Reference Table
Reciprocal & Equivalent Value Scientific Notation
1 Btu (th) 777.648847 ft·lb 7.776 × 10²
5 Btu (th) 3888.244236 ft·lb 3.888 × 10³
10 Btu (th) 7776.488472 ft·lb 7.776 × 10³
50 Btu (th) 38882.442358 ft·lb 3.888 × 10⁴
100 Btu (th) 77764.884717 ft·lb 7.776 × 10⁴
View Complete 15-Row Btu (th) to Foot-pound Table

Real-World Context & Everyday Benchmarks

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To help contextualize these units in everyday life, science, and engineering, here are verified real-world reference points for Foot-pound (ft·lb) and Btu (th) (Btu (th)):

Foot-pound References:

  • Mechanical energy required to raise a one-pound weight vertically by one foot (1.356 J) 1 ft·lb
  • Kinetic energy of a standard 9mm pistol handgun bullet projectile at muzzle 350 ft·lb

Btu (th) References:

  • Thermochemical British Thermal Unit benchmark defined as exactly 1,054.35 J 1 BTU_th

Tap any benchmark above to automatically calculate its exact equivalent in Btu (th).

ISQ Dimension: [M L² T⁻²] Coherent SI Unit: joule (J) Chemical Engineering, Solutions & Physical Chemistry

How to Convert Foot-pound to Btu (th)

Converting Foot-pound (ft·lb) to Btu (th) (Btu (th)) is a core calculation in Energy and Work, which quantifies the physical capacity to perform mechanical work, generate heat, or emit electromagnetic radiation. This calculation navigates the boundary between the International Metric System (SI) and British Imperial / US Customary engineering standards. In contemporary metrology, Imperial units are defined in terms of exact SI standards via international agreements—notably NIST SP 811 and the 1959 International Yard and Pound Agreement. Exactly 1 Foot-pound equals 0.00128593 Btu (th), while 1 Btu (th) equals 777.648847 ft·lb.

Direct Factor1 ft·lb = 0.00128593 Btu (th)
Inverse Ratio1 Btu (th) = 777.648847 ft·lb
Conversion ScaleMetric SI to British Imperial / US Customary Bridge
First-Principles SI Derivation ProofNIST SP 811 / ISO 80000 Compliance

Mathematical Conversion Derivation via Coherent SI Base Unit

Under the International System of Quantities (ISQ), dimensional conversion between non-SI units is rigorously resolved by bridging through the coherent SI base unit (joule (J)) without arbitrary rounding:

Vtarget=Vsource×(ksource→SIktarget→SI)V_{\text{target}} = V_{\text{source}} \times \left( \frac{k_{\text{source} \to \text{SI}}}{k_{\text{target} \to \text{SI}}} \right)
Universal Dimensional Conversion Law (ISO 80000 / NIST SP 811)
1. Source SI Bridge (ksource):1 ft·lb = 1.355818 joule (J)
2. Target SI Bridge (ktarget):1 Btu (th) = 1054.350264 joule (J)
Step-by-step substitution for Foot-pound → Btu (th):V(Btu (th)) = V(ft·lb) × ( 1.355818 / 1054.350264 ) = V(ft·lb) × 0.00128593
Mathematical FormulaValue in Btu (th) = Value in Foot-pound × 0.0012859275Direct computational formula applied for standard conversion.
Worked Example

For an engineering input of 250 ft·lb, applying the conversion factor yields exactly 0.321482 Btu (th). At larger operational scale, 10000 Foot-pound corresponds to 12.859275 Btu (th).

Inverse check: 1 Btu (th) = 777.648847 ft·lb.

Understanding Foot-pound and Btu (th)

Foot-pound

ft·lb
Imperial / US

A Foot-pound (ft·lb) is an imperial and US customary unit for energy and work.

Applications & Practical Context

In practical energy terms, a mechanical energy required to raise a one-pound weight vertically by one foot (1.356 J) equals 1 ft·lb, a kinetic energy of a standard 9mm pistol handgun bullet projectile at muzzle equals 350 ft·lb.

Physical Setup

An energy quantity of 1 ft·lb corresponds to 1.355818 J (performing 1.355818 joules of work or heat transfer).

Conversion to SI Unit: joule (J)
1 ft·lb = 1.355818 J

Btu (th)

Btu (th)
Imperial / US

A Btu (th) is an imperial and US customary unit for energy and work.

Applications & Practical Context

In practical energy terms, a thermochemical British Thermal Unit benchmark defined as exactly 1,054.35 J equals 1 BTU_th.

Physical Setup

An energy quantity of 1 Btu (th) corresponds to 1054.350264 J (performing 1054.350264 joules of work or heat transfer).

Conversion to SI Unit: joule (J)
1 Btu (th) = 1054.350264 J

Domain Metrology & Engineering Applications

Governing Law & Equation

First Law of Thermodynamics (Conservation of Energy: ΔU = Q - W)

Measurement Instrumentation

Rigorously quantified in laboratory and field settings using isoperibol bomb calorimeters, optical laser pulse joulemeters, and digital revenue-grade electric energy meters.

Primary Industry Sectors

Applied across electric power utility metering, thermal energy storage design, chemical plant process enthalpies, and ballistic impact engineering under international metrology standard ISO 80000-5:2019, NIST SP 811.

Physical Orders of Magnitude & Laboratory Reference Benchmarks

Physical Phenomenon / Engineering ReferenceReference ValueConverted to Btu (th)
Mechanical energy required to raise a one-pound weight vertically by one foot (1.356 J)1 ft·lb0.00128593 Btu (th)
Kinetic energy of a standard 9mm pistol handgun bullet projectile at muzzle350 ft·lb0.450075 Btu (th)
Institutional Metrology & Standard Authority:

Formulas, conversion coefficients, and base definitions on this page strictly adhere to the ISO 80000-5:2019, NIST SP 811 and the BIPM SI Brochure (9th Edition). Governed by First Law of Thermodynamics (Conservation of Energy: ΔU = Q - W) under ISO 80000 dimensional vector [M L² T⁻²].

Multi-Variable Engineering Bridge Thermal Enthalpy & Continuous Power

Energy to Continuous Operating Power Bridge (Watts • Kilowatts • Megawatts • Horsepower)

Calculate required average generating or consuming power P = E / t over specified timespans, bridging energy [M L² T⁻²] with continuous power [M L² T⁻³].

P = E / t
Vector: [J] ÷ [s] → [W]
Live Calculated Bridge Equivalent:
1 ft·lb at 1 Hour Continuous Run (3,600 s) = 0.0003766 W
Equals 3.7662 × 10⁻⁷ kW • 3.766161 × 10⁻¹⁰ MW • 5.0505 × 10⁻⁷ hp
SI Power
0.0003766
W
Watts
Grid / Utility
3.7662 × 10⁻⁷
kW
Kilowatts
Power Plant
3.766161 × 10⁻¹⁰
MW
Megawatts
Mechanical Rating
5.0505 × 10⁻⁷
hp
Horsepower (Mechanical)
Metric Horsepower
5.1206 × 10⁻⁷
PS
Metric Horsepower (PS)
HVAC Thermal Rating
0.0013
BTU/h
BTU per Hour
  1. 1. Normalize Input to SI Base Unit (J):
    E = 1 ft·lb × 1.35581795 = 1.35581795 J
  2. 2. Apply Engineering Parameter (t):
    Selected condition: 1 Hour Continuous Run (3,600 s) at t = 3600 s
  3. 3. Execute Governing Physical Law in SI Units:
    P = E / t = (1.35581795 J) ÷ (3600 s) = 0.00037662 W
  4. 4. Convert to Standard Engineering Units:
    • W: 0.00037662 × 1 = 0.0003766 W (Watts) • kW: 0.00037662 × 0.001 = 3.7662 × 10⁻⁷ kW (Kilowatts) • MW: 0.00037662 × 1 × 10⁻⁶ = 3.766161 × 10⁻¹⁰ MW (Megawatts) • hp: 0.00037662 × 0.001341 = 5.0505 × 10⁻⁷ hp (Horsepower (Mechanical)) • PS: 0.00037662 × 0.00136 = 5.1206 × 10⁻⁷ PS (Metric Horsepower (PS)) • BTU/h: 0.00037662 × 3.4121 = 0.0013 BTU/h (BTU per Hour)
Explore Full Power Converter →
Engineering Substance / Operating Standard Parameter Value (s) Reference State / Condition Typical Industrial & Engineering Application
1 Second Instant Discharge 1 1.0 s Peak pulse discharge rating
1 Minute Fast Delivery (60 s) 60 60 s EV fast acceleration or battery boost
1 Hour Continuous Run (3,600 s) 3600 3,600 s (1 hour) Standard 1-hour energy delivery
8 Hours (28,800 s) 28800 28,800 s (8 hours) Single shift continuous draw
24 Hours (86,400 s) 86400 86,400 s (24 hours) Full day steady-state consumption
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Frequently Asked Questions

There are exactly 0.0012859275 btus (th) (Btu (th)) in 1 foot-pound (ft·lb). To calculate larger amounts manually, simply multiply your total number of foot-pounds by the conversion multiplier of 0.0012859275.

The mathematical formula to convert foot-pounds to btus (th) is: [value] * 0.0012859275 = btus (th). Rather than doing the math manually, you can use our high-precision online calculator to process this exact equation instantly without rounding errors.

To perform the reverse calculation from btus (th) back to foot-pounds, you must divide your starting value by 0.0012859275. Our bidirectional tool automatically computes this inverse equation the moment you type into the btu (th) input field.

1 Btu (th) is larger than 1 Foot-pound. Specifically, 1 Foot-pound equals 0.0012859275 btus (th), meaning 1 Btu (th) is 777.6488 times larger than 1 Foot-pound (a difference of 2.89 orders of magnitude). Expressing measurements in foot-pounds requires a larger numerical value to represent the equivalent physical magnitude.

A typical mechanical energy required to raise a one-pound weight vertically by one foot (1.356 J) measures 1 ft·lb, which corresponds to 0.001286 Btu Th (Btu (th)).

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