MEP calculations
that reference the standard

Replace spreadsheets with traceable calculations. Cable sizing, duct sizing, HVAC loads, pipe sizing, drainage, refrigeration — every result linked to BS 7671, CIBSE, ASHRAE or BS EN standards.

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BS 7671:2018+A3:2024CIBSE Guide A + BASHRAE Fund 2021ISO 8528

The problem MEPCalc solves

Spreadsheet chaos

Excel files emailed around, versions colliding, no audit trail. Which version is correct?

Standards uncertainty

Where did this formula come from? Which edition of BS 7671? You're guessing.

Compliance risk

No traceability. Auditors want to know: what standard, what assumption, what date. You can't prove it.

MEPCalc replaces the spreadsheet.

Every calculation traceable to the standard. Every result auditable. Every assumption visible.

50+ calculators across MEP disciplines

Every calculation referenced to the engineering standard

Electrical

  • Cable sizing, voltage drop, fault levels, load schedules, generators, protective devices, EV charging, PV, motor starters, UPS, emergency lighting + more

HVAC & Mechanical

  • Space load (CIBSE A / ASHRAE Fund)
  • Fabric heat loss + solar gains
  • AHU + heat recovery
  • Ductwork sizing + pressure loss
  • Duct + pipe insulation

Ventilation

  • Ventilation design (B2 / Part F / BB101 / HTM 03-01)
  • Natural ventilation (AM10:2026)
  • Whole-dwelling (Part F + SAP 10.3)
  • Standalone fans + acoustic (B4)

Plumbing & Drainage

  • Pipe sizing (CIBSE C / Guide G)
  • Hot/cold water + DHW storage
  • Drainage (EN 12056-2 + Part H)
  • Legionella RA (HSG 274)

Refrigeration

  • Cold-store loads (IOR CoP 2020 / ASHRAE Refrig)
  • Refrigerant pipe sizing (BS EN 12735-1 / ASHRAE Ch.1)
  • Datacentre cooling (TC 9.9 5th ed)
  • Refrigerant data + F-gas register

Acoustic + Renewables

  • Duct noise (CIBSE B4 + BS 848)
  • Solar thermal (BS EN 12976-1 + MCS MIS-3001)

Heating

  • Heat source (BS EN 12828 + CIBSE B1)
  • UFH (BS EN 1264-2:2021)
  • Expansion vessel (BS EN 13831)

How it works

1

Select

Choose the calculator for your task. Browse by discipline or search for the standard you need.

2

Enter

Input your parameters and assumptions. Every field is labelled with the relevant standard reference.

3

Export

Get traceable results with formula breakdown, standard references, and audit trail.

Designed for engineers who care about standards

No shortcuts. No approximations. Just traceable, auditable MEP engineering.

Engineering Standards

Every calculation references the standard

MEPCalc doesn't give you a black-box number. It shows you where every value comes from.

BS 7671:2018+A3:2024

UK Electrical (BS 7671 + IET OSG)

  • Cable sizing
  • Voltage drop
  • Fault levels (App 14)
  • Earthing

CIBSE Guide A:2015

HVAC thermal loads

  • Cooling + heating loads
  • Solar gains
  • Fabric heat loss

CIBSE Guide B (B0–B4) 2016

HVAC systems + ductwork

  • Ductwork (B2)
  • AHU + air conditioning (B3)
  • Acoustic / noise (B4)

IOR Cold Store CoP 2020

Refrigeration design

  • Cold-store loads (Part 3 App A)
  • Door + infiltration
  • Product cooling + respiration

BS EN 12831-1 / 16798-1 / 12735-1 / 378-2

EN harmonised standards

  • Fabric heat load
  • Ventilation IEQ
  • ACR copper tubes
  • Refrigerant safety

ISO 8528-1 / -5

Generator sizing

  • PRP / ESP nameplate (§14.3)
  • Load acceptance (§8.4)
  • Site derating

BS 5422:2023

Pipe + duct insulation

  • Heat loss thickness
  • Condensation risk
  • DHW / chilled / refrigerant

Approved Doc F 2021 + L 2021

UK Building Regs

  • Ventilation rates
  • Energy efficiency
  • Indoor air quality

BS 5266 / EN 1838 / EN 50172

Emergency lighting

  • 1 lx full-width escape route
  • 5-yr photometric verification
  • Open + standby + high-risk

HSG 274 + CIBSE Guide G:2014

Plumbing + water hygiene

  • Pipe sizing (Guide G §6)
  • Hot/cold water (BS EN 806)
  • Legionella RA (HSG 274)

No approximations. No shortcuts.
Every formula is auditable. Every assumption is visible. Every calculation is traceable.

Transparent pricing. No surprises.

Start free for 14 days. No credit card required. Cancel anytime.

Single Module

Pick one calc module

£30/mo

or £299/yr (save £61)

  • Access to one calculator module
  • Full standard references
  • PDF export
Most popular

Single Discipline

All modules in one discipline (HVAC, Electrical, Plumbing, Ventilation, Refrigeration, Heating, or Acoustic + Renewables)

£60/mo

or £549/yr (save £171)

  • All calculators in your chosen discipline
  • Standards references per discipline (BS 7671, CIBSE Guide A/B, IOR, BS EN, ISO, AD-F)
  • Calculation history & audit trail

Full Suite

All 50+ modules across all 7 disciplines

£150/mo

or £1299/yr (save £501)

  • Every calculator across all disciplines
  • Full standards coverage — BS 7671, CIBSE Guide A + B, IOR CoP, BS EN 12831-1 / 16798-1 / 12735-1, ISO 8528, BS 5422:2023, Approved Doc F + L, BS 5266 / EN 1838 / EN 50172, HSG 274
  • Project management & collaboration
  • Calculation history & audit trail

All plans include a 14-day free trial · per seat · no credit card required

Stop emailing spreadsheets.
Start traceable calculations.

7 days free. No credit card. Cancel anytime. MEPCalc is purpose-built for UK MEP engineers.