Calculators

25 articles

BTU to kW Conversion: Quick Reference for Heating Engineers

BTU to kW conversion table, radiator output reference, room heat loss calculation method (1 kW = 3,412 BTU/h)
Cable Voltage Drop Calculator: How to Check Your Circuits Comply

Cable voltage drop calculator: BS 7671 mV/A/m values, 3%/5% limits, worked examples for ring final, shower, cooker circuits
Concrete Volume Calculator: Slabs, Footings & Mix Ratios

Concrete volume calculator: L×W×D formula with 10% waste, C20/C25/C30 mix ratios (1:2:4 = C20), worked examples for patio, strip footing, fence posts, trench fill
Fence Post Depth Calculator: Depth Rules, Post Sizing and Concrete vs Driven Installations

Fence post depth calculator: one-third rule + 150mm (750mm for 1.8m fence), 100×100mm post for 1.8m fence, 300mm minimum concrete collar diameter, BS 8417 UC4 pressure treatment, GPDO 2015 height limits
Grout Quantity Calculator: Tile Size, Joint Width & Coverage

Grout quantity calculator: formula with worked examples for 300×300mm floor, 600×600mm large format, and mosaic tiles
Heat Pump Radiator Output Correction Calculator: Delta-T Correction Factors, MCS Heat Emitter Guide Method and Worked Examples

Delta-T correction factors from BS EN 442, MCS Heat Emitter Guide method, worked example 35/30°C flow/return vs 70/50°C rated, correction factor tables by ΔT
How Do I Calculate How Much Plasterboard I Need for Walls and Ceilings?

Plasterboard quantity calculator: 60 boards/m² standard, waste factors 10–20%, mortar/jointing compound coverage tables
How Do I Calculate Pipe Flow Rates, Velocity & Pressure Drop for Domestic Plumbing?

Pipe flow rate calculator: BS EN 806-3 loading unit method, velocity limits (1–3 m/s copper), pressure drop calculation
How Do I Calculate Staircase Rise, Going, Headroom & Number of Treads?

Staircase calculator: 220mm max rise, 220mm min going, 2000mm headroom, comfort formula 2R+G = 550–700mm per Approved Document K
How Do I Calculate U-Values for Walls, Floors & Roofs?

U-value calculator: worked examples for cavity wall, loft, and ground floor; Approved Document L targets; BS EN ISO 6946 method
How Many Bricks and Blocks Do I Need? Quantity Calculator with Mortar & Waste

Brick and block quantity calculator: 60 bricks/m² half-brick wall, 10 blocks/m² blockwork, mortar coverage tables
How Many Tiles Do I Need? Calculating Quantities with Waste Allowance

Tile quantity calculator: waste percentages by pattern, worked examples, adhesive/grout coverage tables
Max Cable Run Length Calculator: Voltage Drop, Derating & BS 7671 Compliance

Cable run length: BS 7671 voltage drop limits (3% lighting, 5% power), mV/A/m values for T&E cables, derating factors for thermal insulation (0.50), grouping, and temperature
Maximum Demand Calculator: After-Diversity Totals for Domestic Properties

Maximum demand calculator: ADMD with diversity factors from BS 7671 Appendix 1, worked examples including EV charger impact
Mortar Quantity Calculator: Mix Ratios, Bags of Cement and Sand Coverage Tables

Mortar quantity calculator: 0.016m³/m² half-brick walling (1:5 mix), 0.030m³/m² one-brick, 0.002–0.003m³/m² repointing, 7–8 bags cement per m³ at 1:5, BS EN 998-2 Designation M4
Paint Coverage Calculator: Litres Needed by Wall Area & Coats

Paint coverage calculator: 12–14 m²/L sealed emulsion, 6–8 m²/L new plaster, worked examples for bedroom re-paint, new plaster, exterior masonry, and woodwork
Plaster Quantity Calculator: Bags Per Square Metre by Coat Thickness

Plaster quantity calculator: bags per m² for Thistle Bonding (5m²/bag), MultiFinish (18m²/bag), sand/cement render worked examples
Radiator BTU Calculator: Room Size, Windows, Insulation & Exposure

Radiator BTU/W calculator: heat loss factors 40–130 W/m² by insulation level, ΔT50 output correction for heat pumps, K1/K2/K3 output table, worked sizing examples
Room Heat Loss Calculator: Detailed Method Using U-Values, CIBSE Guide A and Worked Examples

Room heat loss calculator: fabric (U×A×ΔT) plus ventilation (0.33×N×V×ΔT) with worked example; design temperatures; heat pump vs gas radiator sizing comparison
Room Heat Loss Calculator: W/m² Method, Worked Examples & Radiator Sizing

Heat loss calculator: simplified W/m³ method (25–100 W/m³), element-by-element U-value×area×ΔT method, design temperatures, radiator ΔT50 ratings, heat pump correction factors
Room Volume Calculator: Air Change Rates, MVHR Sizing and Ventilation Worked Examples

Room volume calculator: L×W×H formula, Part F 2021 (0.3 l/s/m² floor area background ventilation), MVHR sizing worked example (3-bed, 50 l/s), commissioning tolerance ±10%, ACH to l/s conversion
Screed Depth Calculator: Sand/Cement vs Liquid Screeds, Drying Times and Moisture Testing

Screed depth calculator: 65–75mm sand/cement floating, 30mm anhydrite minimum, 30mm cover above UFH pipe crown, BS 8204 standard, drying rate 1mm/day, ≤75% RH hygrometer threshold before flooring
Soakaway Sizing Calculator: BRE Digest 365 Percolation Test Method, Volume Calculation Formula and Worked Examples

BRE Digest 365 percolation test Vp calculation, As = Vp × D × r × A / 2 formula, worked example for 80m² roof catchment in sandy loam, crate vs rubble comparison
Three-Phase Voltage Drop Calculator: BS 7671 Method, Balanced and Unbalanced Loads, Worked Examples

Three-phase voltage drop: BS 7671 mV/A/m method, balanced and unbalanced loads, power factor correction, worked motor supply example, cascaded circuit voltage drop budgeting
Timber Joist Calculator: Span Tables, Spacing & Load Requirements

Timber joist calculator: C16/C24 span tables at 400/450/600mm centres, notching and drilling rules, strutting requirements, worked examples for extension floor and loft conversion