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Life Cycle Assessment Calculator

Estimate whole-building life-cycle carbon emissions (kgCO2e) across product, construction, use, and end-of-life stages per ISO 14040.

About this calculator

Floor Area (sq ft) is the one number every stage of this calculator passes through -- it scales the embodied-materials side (A1-A3 Product Stage carbon is Floor Area times Embodied Carbon Rate, and A4-A5, B1-B5, and C1-C4 all derive as percentages of that same A1-A3 figure) AND the operational-energy side (annual operational energy converts your Operational EUI per square foot into total building energy by multiplying by Floor Area too), so a change in Floor Area moves Total Life-Cycle Carbon (kgCO2e) more than an equal percentage change in any single-side input like Grid Carbon (kgCO2e/kWh) or Embodied Carbon Rate, both of which only touch one side of the split. At this calculator's defaults, the B6 Operational Carbon term -- Operational EUI converted to kWh, multiplied by Grid Carbon intensity, then multiplied across the full Study Period -- makes up roughly seven-eighths of Total Life-Cycle Carbon, so Study Period, Operational EUI, and Grid Carbon Intensity each move the total by a comparable amount to one another (they combine multiplicatively inside the same B6 term), while Embodied Carbon Rate only moves the smaller embodied-side total.

Embodied Share (%) and Operational Share (%) always sum to 100% by construction, since one is defined as the complement of the other over Total Life-Cycle Carbon.

Inputs

sq ft
%
%
%

Results

Total Life-Cycle Carbon (kgCO2e)

1,999,999

Total Embodied Carbon (kgCO2e)241,500
Operational Carbon (kgCO2e)1,758,499
Embodied Share (%)12.1%
Operational Share (%)87.9%
Carbon Intensity (kgCO2e/ft²/yr)6.67
Total Life-Cycle Energy (MJ)17,758,495
How to Use This Calculator
  1. Enter Floor Area in sq ft and Study Period in years (LEED uses 60 years).
  2. Enter Embodied Carbon Rate in kgCO2e/ft² and Construction Carbon as a percentage of A1–A3.
  3. Enter Annual Operational EUI in kBtu/ft²/yr and Grid Carbon Intensity in kgCO2e/kWh.
  4. Enter Maintenance/Replacement and End-of-Life carbon percentages.
  5. Review Total Life-Cycle Carbon, Embodied vs Operational Carbon split, and Carbon Intensity per ft² per year.

How the result changes with Floor Area (sq ft)

Floor Area (sq ft)Total Life-Cycle Carbon (kgCO2e)
2,5001,000,000
3,7501,500,000
7,5002,999,999
12,5004,999,999

What each input means

Floor Area (sq ft)
Total building floor area in square feet.
Study Period (years)
Life-cycle assessment study period. LEED uses 60 years; BREEAM uses 60-120 years.
Embodied Carbon (kgCO2e/ft²)
A1-A3 embodied carbon per sq ft. Steel frame ~40-50, concrete ~30-45, mass timber ~15-25.
Construction Carbon (% of A1-A3)
A4-A5 stage carbon as a percentage of product stage. Typically 3-8%.
Operational EUI (kBtu/ft²/yr)
Annual energy use intensity. Office ~50-80, home ~30-50, hospital ~150-250.
Grid Carbon (kgCO2e/kWh)
Electricity grid carbon intensity. US avg ~0.4, France ~0.05, coal-heavy ~0.8-1.0.
Maintenance/Replacement (% of A1-A3)
B1-B5 maintenance and replacement carbon over the full study period as % of initial embodied.
End of Life (% of A1-A3)
C1-C4 demolition and disposal carbon as % of initial embodied. Typically 2-5%.

What each result means

Total Life-Cycle Carbon (kgCO2e)
Whole-building GWP across all life-cycle stages.
Total Embodied Carbon (kgCO2e)
Sum of A1-A5, B1-B5, and C1-C4 stages.
Operational Carbon (kgCO2e)
B6 stage: operational energy carbon over the study period.
Embodied Share (%)
Percentage of total carbon from embodied sources.
Operational Share (%)
Percentage of total carbon from operational energy.
Carbon Intensity (kgCO2e/ft²/yr)
Annualized carbon per square foot over the study period.
Total Life-Cycle Energy (MJ)
Combined embodied and operational energy over the study period.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Floor Area (sq ft) = 5000, Study Period (years) = 60, Embodied Carbon (kgCO2e/ft²) = 35, Construction Carbon (% of A1-A3) = 5 = 8 input(s) provided
  2. Calculate Total Life-Cycle Carbon
    Total Life-Cycle Carbon = a1a3Carbon + a4a5Carbon + b1b5Carbon + b6Carbon + c1c4Carbon
    1999999 = 1999999
  3. Calculate Total Embodied Carbon
    Total Embodied Carbon = a1a3Carbon + a4a5Carbon + b1b5Carbon + c1c4Carbon
    241500 = 241500
  4. Calculate Operational Carbon
    Operational Carbon = annualOperationalCarbon * studyPeriod
    1758499 = 1758499

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.

Frequently Asked Questions

Why does Floor Area move Total Life-Cycle Carbon more than Grid Carbon Intensity does?

Grid Carbon Intensity only feeds the B6 Operational Carbon term. Floor Area feeds BOTH sides at once -- it scales A1-A3 Product Stage carbon (and everything derived as a percentage of it: A4-A5, B1-B5, C1-C4) on the embodied side, and it also multiplies annual operational energy on the operational side. Because Floor Area touches every single term in the whole-life total simultaneously, the same percentage change moves Total Life-Cycle Carbon (kgCO2e) further than a change confined to just the operational side.

Why do Study Period, Operational EUI, and Grid Carbon Intensity all move the total by a similar amount?

All three combine multiplicatively inside the same B6 Operational Carbon term -- annual operational energy (from Operational EUI and Floor Area) times Grid Carbon Intensity times Study Period. A given percentage increase in any one of the three produces the same percentage increase in B6 Operational Carbon, so at this calculator's defaults, where B6 makes up roughly seven-eighths of Total Life-Cycle Carbon, all three move the grand total by a comparable share.

Does Grid Carbon Intensity affect Embodied Carbon at all?

No -- Total Embodied Carbon is the sum of A1-A3, A4-A5, B1-B5, and C1-C4, none of which reference Grid Carbon (kgCO2e/kWh) anywhere in the calculation. Grid Carbon Intensity only enters through B6 Operational Carbon, so changing it moves Operational Carbon (kgCO2e) and, through the total, Operational Share (%), but leaves Total Embodied Carbon (kgCO2e) completely unchanged.

Why do Embodied Share (%) and Operational Share (%) always add up to 100%?

They are defined as complements of each other over the same denominator: Embodied Share (%) is Total Embodied Carbon divided by Total Life-Cycle Carbon, and Operational Share (%) is Operational Carbon (B6) divided by that identical total -- and Total Life-Cycle Carbon is defined as exactly the sum of the embodied total and B6. There is no third category left over, so the two shares can never do anything but sum to 100%.

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