Calculators
Every calculator, and the standard behind it
That count is the calculators available on a paid plan. It excludes unreleased calculators still in testing, and superseded pages kept reachable so existing saved sheets still open.
Electrical
Distribution design to BS 7671 and the IET On-Site Guide, plus the plant that hangs off it.
Circuit Design
Sizes the cable, checks the adiabatic condition, selects the protective device and verifies earth-fault loop impedance in one pass.
BS 7671
Voltage Drop
Volt drop along a circuit from the tabulated mV/A/m figures, with the reactive term where it matters.
BS 7671 Appendix 4
Fault Level
Prospective fault current at a point in the installation, single- and three-phase.
BS 7671 Appendix 14
Load Schedule
Connected load and maximum demand for an installation, applying the tabulated diversity factors.
IET On-Site Guide Table A2
DB Schedule
Builds a distribution board schedule circuit by circuit from the load schedule.
BS EN IEC 61439-1
Motor Starter
Contactor and overload selection for direct-on-line and star-delta starting.
IEC 60947-4-1
Power Factor Correction
Capacitor bank size to reach a target power factor, with the resulting kVA saving.
BS 7671 / CTG007
Generator
Generator set sizing including step-load acceptance and the resulting voltage and frequency dip.
ISO 8528-1 / -5
UPS
UPS rating and autonomy from the connected load and the required runtime.
IEC 62040-3:2021
Lighting Design
Luminaire count and spacing by the lumen method for a target maintained illuminance.
BS EN 12464-1:2021
Emergency Lighting
Escape-route and open-area coverage, spacing and duration for an emergency scheme.
BS 5266-1:2025 / BS EN 1838:2024
EV Charging
Charge-point load, diversity and the protective measures a charging installation needs.
BS 7671 Section 722
HVAC and refrigeration
Heating and cooling loads by the CIBSE or ASHRAE method, and the refrigeration plant that serves them.
Space Load
Room heating and cooling loads, by the cyclic admittance method or the radiant time series.
CIBSE Guide A / ASHRAE Fundamentals
Fabric Heat Loss
Design heat loss including the thermal-bridging allowance and adjacency factors.
BS EN 12831-1:2017
Solar Gain
Solar heat gain through glazing for a given station, orientation and shading.
CIBSE Guide A
Refrigeration Loads
Cold-store load build-up: transmission, infiltration, product, and internal gains.
IOR Cold Store CoP 2020 / ASHRAE
Refrigerant Pipe Sizing
Suction, discharge and liquid line sizes against pressure drop and oil-return velocity.
ASHRAE Refrigeration 2022
Condensate Drain
Condensate flow and drain size for cooling coils, with trap depth.
AD H / BS EN 12056-2
Machinery Room
Machinery-room ventilation and leak detection for a refrigerant charge.
BS EN 378-3
Ventilation and ductwork
Air rates, duct sizes and the pressure and noise that follow from them.
Ventilation Design
Supply and extract rates for a space, by occupancy, area or air-change basis.
CIBSE Guide B2 / AD F / BS EN 16798-1
Whole Dwelling
Whole-dwelling and room extract rates for a residential scheme.
Approved Document F 2026
Natural Ventilation
Opening areas and achievable flow from wind and buoyancy.
BS EN 16798-7
AHU Duty
Air-handling unit duty, coil loads and heat-recovery performance.
CIBSE Guide B3
Standalone Fan
Fan duty and specific fan power against the Part L limit, or the fan energy index.
Approved Document L / AMCA 208
Duct Sizing
Duct sizes by constant pressure drop or velocity, circular, rectangular or flat-oval.
CIBSE Guide B2 / Guide C
Ductwork Pressure Loss
System pressure loss along an index run, straight lengths plus the fitting catalogue.
CIBSE Guide C
Duct Insulation
Insulation thickness for heat loss, condensation control or personnel protection.
BS 5422:2023
Grille
Grille free area, face velocity and throw for a required flow.
CIBSE Guide B2
Louvre
Louvre free area and pressure drop for intake and discharge openings.
CIBSE Guide C
Duct Noise
Breakout and regenerated noise along a duct run, to a room NR level.
CIBSE Guide B4
Heating, pipework and plumbing
Wet systems end to end: heat source, distribution, storage and drainage.
Heat Source Sizing
Boiler or heat-pump duty from the building load, with margins and sequencing.
CIBSE Guide B1 / AM16
Underfloor Heating
Floor output and pipe spacing against the surface-temperature limits.
BS EN 1264-2:2021
Expansion Vessel
Vessel volume and charge pressure from system volume and temperature range.
BS EN 12828 Annex D
Hydronic Pipe Sizing
Heating and chilled pipe sizes against pressure drop and velocity limits.
CIBSE Guide C
Pipe Insulation
Insulation thickness for heat loss, freeze and condensation control.
BS 5422:2023
Cold Water Pipe Sizing
Cold water pipe sizes from loading units, with demand and velocity checks.
CIBSE Guide G
Hot Water Storage
Storage volume and recovery for a building's hot water demand profile.
CIBSE Guide G
Drainage
Above and below-ground drainage sizes from discharge units and gradient.
BS EN 12056 / AD H
Legionella Risk Assessment
Design-stage legionella risk assessment for a hot and cold water system.
HSG274 Part 2 / L8
Renewables
Solar output by the SAP method, with the MCS and connection thresholds.
Solar Thermal
Annual solar contribution to hot water by the SAP monthly method.
SAP 10.3 Appendix H / MCS MIS 3001
PV Sizing
Array yield, specific yield and inverter current, against the G98 and G99 thresholds.
SAP 10.3 Appendix M / MCS MIS 3002
See the working before you trust it
For several of these we publish our own verification: fixed worked examples run through the same calculation code, compared line by line with the values printed in the standard, with every delta and pass or fail shown.
MEPCalc is in a closed tester phase ahead of public launch.