Roofing Calculators
Calculate tiles, felt, battens, guttering and all roofing materials for UK roof types.
Roof Tile Calculator
Calculate how many roof tiles you need per m² for your roof.
Ridge Tile Calculator
Work out ridge tile quantities and mortar needed.
Felt and Batten Calculator
Calculate roofing felt and batten quantities for your roof.
Soffit and Fascia Calculator
Work out soffit board and fascia lengths needed.
Gutter Sizing Calculator
Calculate gutter size and downpipe requirements for your roof area.
Lead Flashing Calculator
Calculate lead flashing quantities for valleys, abutments and chimneys.
Roof Area Calculator
Calculate actual roof area from plan dimensions and pitch angle.
Roof Pitch Calculator
Calculate roof pitch angle from rise and run measurements.
Roof Truss Calculator
Estimate truss quantities and spacing for your roof span.
Flat Roof Membrane Calculator
Calculate membrane and insulation needed for flat roof coverings.
Roof Ventilation Calculator
Calculate roof ventilation to comply with UK Building Regulations and BS 5250.
Roof Window Sizing Calculator
Calculate Velux or roof window size and quantity for Part L daylight compliance.
Fascia Board Calculator
Calculate fascia boards, corner trims and fixings for roof perimeter.
Gutter Bracket Calculator
Calculate gutter brackets, outlets, corners and union joints for guttering installation.
Dry Ridge System Calculator
Calculate dry ridge system unions, end caps, roll and gasket by tile profile.
Dry Verge Calculator
Calculate dry verge units, starter kits and end caps from gable length.
Hip Tile Calculator
Calculate hip tile quantities, hip irons and mortar from roof geometry.
Valley Trough Calculator
Calculate valley trough lengths in GRP or lead with overlap and tile-and-a-half count.
Flat Roof Fall Calculator
Calculate firring strip dimensions for flat roof falls at 1:40, 1:60 or 1:80 gradients.
EPDM Rubber Roof Calculator
Calculate EPDM single-ply membrane, adhesive, perimeter trim and water check strips.
GRP Flat Roof Calculator
Calculate GRP fibreglass roof resin, CSM mat, trims and catalyst ratios.
Chimney Flashing Calculator
Calculate lead code, apron, step and back gutter flashing from chimney dimensions.
Slate Roof Calculator
Calculate slate quantities from headlap and gauge with nail count and battens.
Roof Insulation Calculator
Calculate roof insulation thickness by type to achieve target U-values.
Solar Panel Roof Loading Calculator
Check solar panel weight and wind uplift against rafter capacity.
Zinc Standing Seam Calculator
Calculate zinc standing seam sheet widths, clips, underlayer and drip edges.
Roof Lantern Calculator
Calculate roof lantern structural opening, kerb depth and glazing bar spacing.
Roof Snow Load Calculator
Calculate roof snow loads per BS EN 1991-1-3 by altitude and zone.
Roof Wind Load Calculator
Calculate roof wind loads per BS EN 1991-1-4 with pressure coefficients by zone.
Eaves Ventilation Calculator
Calculate eaves ventilation area per BS 5250 with soffit vent and ridge vent pairing.
30 free calculators in Roofing
Roofing Materials and Regulations in the UK
Roofing in the UK must withstand the country's varied and often harsh weather conditions, from driving rain in the west to heavy snowfall in Scotland and high winds along coastal areas. The choice of roofing materials, underlays, and fixings must account for local exposure zones as defined in BS 5534 (the British Standard for slating and tiling) and BS 8104 for wind-driven rain exposure. Our roofing calculators help you quantify materials accurately for any UK roof type, from traditional pitched slate to modern flat roof membranes.
Concrete roof tiles remain the most popular choice for UK new-builds and re-roofs, with Marley, Redland (now BMI), and Russell being the dominant manufacturers. Common profiles include the Marley Modern (plain interlocking tile at approximately 10 tiles per m²), the Redland 49 (a large format tile at roughly 10 tiles per m²), and traditional plain tiles which require around 60 tiles per m² due to their smaller size and double-lap fixing. Our roof tile calculator accounts for tile type, roof area, and wastage to give an accurate order quantity.
Under UK Building Regulations (Approved Document C), roofs must prevent moisture ingress and provide adequate ventilation. Roofing underlay (breathable membrane) must comply with BS 5250, and battens are typically 25mm × 50mm treated softwood fixed at gauge spacings specified by the tile manufacturer. The felt and batten calculator works out underlay rolls and batten linear metres based on your roof area and tile gauge. Ridge tiles, dry ridge systems (now increasingly specified over traditional mortar bedding), hip tiles, and valley troughs must also be quantified for a complete roofing order.
Flat roofs in the UK are regulated under Approved Document C and must achieve a minimum fall of 1:80 (with 1:40 being the recommended design fall to allow for construction tolerances). Common flat roof covering systems include EPDM rubber membrane (such as ClassicBond or Firestone), GRP fibreglass (Fibreglass Flat Roofing from Topseal or Cure It), and torch-on felt (SBS modified bitumen). Our flat roof membrane calculator helps estimate the membrane area, insulation, and trims needed for flat roof projects.
Lead work remains essential in UK roofing, particularly for flashings at abutments, chimneys, valleys, and dormer cheeks. Lead sheet is specified by code number (Code 3 to Code 8) with Code 4 being the most common for flashings and Code 5 for valleys. All lead work should follow the Lead Sheet Association guidelines and be installed by competent roofers to ensure longevity and weather-tightness.