HomeCostNest guides
How HomeCostNest Calculates Project Costs
HomeCostNest uses project inputs, market-specific cost benchmarks, reviewed methodology, project adjustments, and documented planning assumptions to produce Low, Typical, and High planning estimates.
10 calculators
20 US & UK profiles
Market-specific methodology
Reviewed September 2026
How our estimates work
- 1. Choose a project
- 2. Select market
- 3. Enter details
- 4. Apply benchmark and adjustments
- 5. Review planning range
Project inputs → market profile → cost benchmark → adjustments → estimate.
Low, Typical, and High
Low is a lower-cost planning scenario. Typical is a practical reference estimate; depending on the calculator it may be a published typical benchmark, a midpoint of a reviewed range, or a documented HomeCostNest planning convention. High reflects upper ranges, higher specification, complexity, or supported additional work. These are planning ranges, not contractor quotations.
United States and United Kingdom methodology
United States
USD ($) · common unit: sq ft · US terminology · US-specific reviewed profiles.
United Kingdom
GBP (£) · common unit: m² · UK terminology · UK-specific reviewed profiles.
Markets are not simple currency conversions. Each profile can use different benchmarks, units, terminology, project options, assumptions, methodology, and source metadata.
How to read benchmark tables
Values are planning benchmarks and the unit matters. Installed ranges may already include normal labour or installation. Optional additions are only combined where the calculator methodology does so; they should not be added together independently.
Driveway Cost Calculator US · UK
Heat Pump Cost Calculator US · UK
United States
USD · sq ft · The installed system type establishes the base range. Equipment tier and selected ductwork are shown separately; ductwork should not be selected for ductless systems.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Air-source / whole-home | $8,000 | $10,500 | $20,000 | installed system / project range |
| Ductless mini-split | $2,000 | $9,500 | $17,000 | installed system / project range |
| Geothermal | $20,000 | $35,000 | $50,000 | installed system / project range |
Adjustments / add-ons: Equipment tier, New/replacement ductwork
HomeCostNest planning assumptions: Home size is rough planning context only; it does not determine equipment sizing. Professional sizing requires an ACCA Manual J load calculation. Permits may add roughly $50–$300 depending on jurisdiction.
Sources: Angi 2026; HomeGuide 2026; This Old House 2026; ENERGY STAR · Last reviewed: 2026-09-19
United Kingdom
GBP · m² · System type establishes the UK project range. Selected radiators, underfloor heating, and pipework are isolated allowances. Estimates are before any grant and home size does not determine final kW sizing.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Air-to-water ASHP | £11,000 | £15,000 | £20,000 | installed system / project range |
| Air-to-air ASHP | £2,000 | £3,000 | £4,000 | installed system / project range |
| Ground source heat pump | £18,000 | £34,000 | £50,000 | installed system / project range |
Adjustments / add-ons: Larger radiators (around 10), Underfloor heating, Heating pipework replacement
HomeCostNest planning assumptions: Pipework bounds are a HomeCostNest planning assumption around the reviewed £2,000 allowance. Insulation upgrades are not included. Boiler Upgrade Scheme support is not subtracted because eligibility can change.
Sources: Checkatrade — Air Source Heat Pump Costs UK 2026 (updated May 2026); Ground Source Heat Pump Cost 2026 (updated August 2026); Cost to Replace Boiler With Heat Pump 2026 (updated August 2026) · Last reviewed: 2026-09-20
Bathroom Remodel Cost Calculator US · UK
United States
USD · sq ft · Bathroom area uses the selected installed scope range. Finish and special selections are modest HomeCostNest planning allowances; ordinary fixtures are already represented in broad remodel ranges.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Minor renovation | $0 | $0 | $0 | per sq ft |
| Partial remodel | $50 | $100 | $150 | per sq ft |
| Full remodel | $150 | $250 | $350 | per sq ft |
Adjustments / add-ons: Finish level, Special shower installation, Heated floor upgrade, Major layout / plumbing changes
HomeCostNest planning assumptions: Typical is the midpoint of supplied installed ranges, not a published national average. Permits are not included and local requirements vary.
Sources: HomeGuide 2026; Angi 2026; This Old House 2026 · Last reviewed: 2026-09-19
United Kingdom
GBP · m² · The reviewed UK full-bathroom project range is the baseline. Size bands, finish, and layout changes are modest HomeCostNest planning assumptions; only explicit special work is added to avoid double-counting ordinary fixtures.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Small / compact bathroom | £1,200 | £3,600 | £6,000 | installed system / project range |
| Standard bathroom | £1,500 | £4,500 | £7,500 | installed system / project range |
| Large bathroom | £1,800 | £5,400 | £9,000 | installed system / project range |
Adjustments / add-ons: Finish quality, Plumbing / layout change, Walk-in shower upgrade, Standard shower installation, Bath installation
HomeCostNest planning assumptions: Compact and large size bands are HomeCostNest planning adjustments around the published national project range. Finish and layout adjustments are isolated planning assumptions. Ordinary shower and bath replacement are already represented by the broad remodel baseline.
Sources: Checkatrade — Bathroom Remodel Cost UK 2026 (updated May 2026) · Last reviewed: 2026-09-20
Roof Replacement Cost Calculator US · UK
United States
USD · sq ft · Roof area is multiplied by installed material rates. Removal, limited decking repair, and access are separate allowances; decking does not assume the whole roof needs replacement.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Architectural asphalt | $0 | $0 | $0 | per sq ft |
| Asphalt 3-tab | -$1 | -$1 | -$1 | per sq ft |
| Metal | $1 | $6 | $10 | per sq ft |
| Tile | $3 | $11 | $19 | per sq ft |
| Natural slate | $6 | $15 | $24 | per sq ft |
Adjustments / add-ons: Old-roof removal, Some decking repair, Roof pitch, Complex roof / access
HomeCostNest planning assumptions: Material-specific tear-off allowances should be refined further in a later dataset update. Steep pitch and complex access are modest HomeCostNest planning adjustments. Permits are not included; they commonly vary roughly $100–$500.
Sources: HomeGuide 2026 Roof Replacement; HomeGuide 2026 Tear Off and Replace · Last reviewed: 2026-09-19
United Kingdom
GBP · m² · Roof area is multiplied by selected supply-and-fit material rates. Roof shape is a modest context adjustment rather than a second installed-rate baseline. Scaffolding and skip hire appear only when selected; structural repairs and other roof works are excluded.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Natural slate | £160 | £218 | £275 | per m² |
| Plain concrete tiles | £120 | £175 | £230 | per m² |
| Clay tiles | £160 | £218 | £275 | per m² |
| Flat EPDM / rubber | £80 | £90 | £100 | per m² |
Adjustments / add-ons: Roof shape / complexity context, Two-storey semi scaffolding, Include skip hire
HomeCostNest planning assumptions: Roof-shape adjustments are calibrated HomeCostNest planning context, not a second full roof-type rate. Relevant source tables may be quoted +VAT; VAT treatment should be confirmed with the installer. Insulation, rafters/trusses, leadwork, fascias, soffits, and rainwater goods are not included.
Sources: Checkatrade — Roof Replacement Cost Breakdown 2026 (updated March 2026); Roof Installation Cost Guide 2026 (updated June 2026) · Last reviewed: 2026-09-20
Window Replacement Cost Calculator US · UK
United States
USD · windows · Installed style is the base range. Frame, glass, installation, and access are isolated planning adjustments to avoid stacking duplicate full-window costs.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Double-hung | $0 | $0 | $0 | per windows |
| Single-hung | -$50 | -$225 | -$400 | per windows |
| Casement | $50 | $275 | $500 | per windows |
| Awning | $50 | -$225 | -$500 | per windows |
| Picture | -$50 | -$625 | -$1,200 | per windows |
| Bay | $1,650 | $2,575 | $3,500 | per windows |
| Bow | $2,650 | $4,075 | $5,500 | per windows |
Adjustments / add-ons: Frame material, Glass specification, Full-frame replacement, Difficult second-storey access
HomeCostNest planning assumptions: Low-E uses a 10% / 15% / 20% HomeCostNest application of supplied guidance. Frame and full-frame adjustments are HomeCostNest modeling assumptions. Permits are not included; opening-size changes may require them.
Sources: HomeGuide 2026; Angi 2026 · Last reviewed: 2026-09-19
United Kingdom
GBP · windows · The selected installed window style establishes the per-window range. Aluminium, timber, and triple glazing use isolated calibrated percentage adjustments so full style costs are not double-counted. Full-frame work and access are shown separately.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| uPVC casement | £0 | £0 | £0 | per windows |
| Sash | £250 | £800 | £1,230 | per windows |
| Bay | £650 | £1,500 | £1,830 | per windows |
| Bow | £750 | £1,150 | £1,730 | per windows |
Adjustments / add-ons: Frame material, Glazing, Full-frame installation, Difficult upper-storey access
HomeCostNest planning assumptions: Aluminium and timber premiums are HomeCostNest calibrated planning assumptions around published guidance. Triple glazing is a premium adjustment, not an additional £1,200 full-window cost. FENSA/Certass and building compliance should be confirmed with the installer.
Sources: Checkatrade — New Windows Cost Guide & Calculator 2026 (updated July 2026); Cost of Replacing Sash Windows 2026 (updated June 2026); Flush Casement Window Costs 2026 (updated July 2026) · Last reviewed: 2026-09-20
HVAC Replacement Cost Calculator US · UK
United States
USD · sq ft · Installed system type establishes the base range. Equipment tier, ductwork, and thermostat are separate allowances; home size is a context cross-check only.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Furnace + central AC | $5,000 | $8,000 | $11,000 | installed system / project range |
| Central AC only | $3,300 | $5,950 | $8,300 | installed system / project range |
| Furnace only | $2,000 | $3,700 | $5,400 | installed system / project range |
Adjustments / add-ons: Equipment tier, New/replacement ductwork, Include thermostat
HomeCostNest planning assumptions: Final HVAC sizing should be based on a professional load calculation. Equipment tier adjustments are HomeCostNest planning assumptions, not national averages. Permits are not included and vary by jurisdiction.
Sources: HomeGuide 2026 HVAC; HomeGuide 2026 Ductwork; Angi 2026 HVAC and AC; ENERGY STAR · Last reviewed: 2026-09-19
United Kingdom
GBP · m² · The selected system type determines the full UK baseline; the HVAC replacement range is not mixed with central-heating installation ranges. Selected additional pipework, radiators, and controls are isolated allowances.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Existing HVAC heating/cooling replacement | £5,000 | £7,250 | £10,000 | installed system / project range |
| Gas central heating | £4,500 | £5,250 | £6,000 | installed system / project range |
| Electric central heating | £3,230 | £3,790 | £4,350 | installed system / project range |
| Oil central heating | £5,000 | £6,150 | £7,300 | installed system / project range |
Adjustments / add-ons: Additional pipework / radiators, Heating controls upgrade
HomeCostNest planning assumptions: The HVAC replacement low and high bounds are HomeCostNest planning bounds around the reviewed £7,250 typical benchmark. Normal system-level radiators and pipework are not added again. Final capacity should be determined by a professional design, not property area alone.
Sources: Checkatrade — HVAC Cost UK 2026 (updated May 2026); Central Heating Installation Cost UK 2026 (updated May 2026) · Last reviewed: 2026-09-20
Garage Conversion Cost Calculator US · UK
United States
USD · sq ft · Garage floor area uses the reviewed US conversion-to-living-space planning range. Detached garages, bathrooms, kitchens, and structural work are shown separately; choose only one kitchen option.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Attached / integral garage | $0 | $0 | $0 | planning adjustment |
| Detached garage | $0 | $0 | $0 | planning adjustment |
Adjustments / add-ons: Add bathroom, Kitchen option, Structural condition
HomeCostNest planning assumptions: Detached-garage adjustment is a HomeCostNest planning assumption. Major structural uncertainty can materially change the estimate after professional inspection. Permits, design, major foundation reconstruction, service upgrades, engineering, and extensive utility relocation are excluded.
Sources: HomeCostNest reviewed US V1 planning dataset · Last reviewed: 2026-09
United Kingdom
GBP · m² · Floor area uses reviewed per-m² conversion rates. Garage type is a transparent calibrated per-m² adjustment; bathroom and kitchen are explicit add-ons only.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Integral | £0 | -£188 | -£375 | per m² |
| Attached | £0 | £0 | £0 | per m² |
| Detached | £313 | £313 | £313 | per m² |
Adjustments / add-ons: Add bathroom, Add kitchen, Additional structural work
HomeCostNest planning assumptions: Structural allowance is a HomeCostNest planning assumption. Building Regulations and planning fees are not included.
Sources: Checkatrade Garage Conversion Cost 2026 · Last reviewed: 2026-09-19
Loft Conversion Cost Calculator US · UK
United States
USD · sq ft · Finished attic area uses the reviewed US planning range. Dormer or major roof work, a bathroom, permanent stairs, and reinforcement are explicit selections; major roof modification should not be stacked with another major structural allowance.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Basic existing-roof conversion | $0 | $0 | $0 | per sq ft |
| Dormer addition | $5,000 | $15,000 | $30,000 | per sq ft |
| Major roof modification | $15,000 | $35,000 | $60,000 | per sq ft |
Adjustments / add-ons: Add bathroom, New permanent staircase, Additional reinforcement
HomeCostNest planning assumptions: Feasibility depends on headroom, floor structure, stairs, egress, insulation, electrical/HVAC, and local requirements. This calculator does not determine code compliance. Permits, design, and unusual structural engineering are excluded.
Sources: HomeCostNest reviewed US V1 planning dataset · Last reviewed: 2026-09
United Kingdom
GBP · m² · Type-specific rates are derived systematically from supplied 30m² project ranges. Ensuite and exceptional structural conditions are separate allowances.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Velux / rooflight | £0 | £0 | £0 | per m² |
| Dormer | £583 | £750 | £1,000 | per m² |
| Hip-to-gable | £917 | £1,083 | £1,333 | per m² |
| Modular | £250 | £583 | £1,000 | per m² |
| Mansard | £917 | £1,250 | £1,667 | per m² |
| Shell | £0 | £83 | £250 | per m² |
Adjustments / add-ons: Add bathroom / ensuite, Exceptional structural conditions
HomeCostNest planning assumptions: Roof structure, staircase, steelwork, access and specification can materially affect quotes. Building Regulations fees are not included.
Sources: Checkatrade Loft Conversion Cost 2026 · Last reviewed: 2026-09-19
House Extension Cost Calculator US · UK
United States
USD · sq ft · Total new finished floor area uses the reviewed US home-addition per-square-foot range. The selected scope is an alternative area profile, while kitchen, bathroom, and explicitly selected reinforcement are separate allowances.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Standard finished room addition | $0 | $0 | $0 | per sq ft |
| Basic / simple addition | -$25 | -$75 | -$150 | per sq ft |
| Higher-spec / complex addition | $75 | $100 | $100 | per sq ft |
Adjustments / add-ons: Add kitchen fit-out, Add bathroom, Additional structural reinforcement
HomeCostNest planning assumptions: Enter total floor area for all storeys; no generic two-storey multiplier is added. Architect/designer and engineering fees, permits, zoning, utility relocation, unusual foundations, demolition, and financing are excluded. Typical is a HomeCostNest planning midpoint, not automatically a published national average.
Sources: HomeCostNest reviewed US V1 planning dataset · Last reviewed: 2026-09
United Kingdom
GBP · m² · Total new floor area uses reviewed full-extension rates excluding VAT. A two-storey project uses the same per-m² benchmark when total floor area is entered; kitchen and bathroom are explicit add-ons.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Functional full extension | £0 | £0 | £0 | per m² |
| Shell only | -£600 | -£950 | -£1,300 | per m² |
Adjustments / add-ons: Add kitchen, Add bathroom
HomeCostNest planning assumptions: Base extension benchmark excludes VAT. Professional fees, planning, Building Control, party-wall, ground conditions and unusual structural work are excluded.
Sources: Checkatrade House Extension Cost 2026 · Last reviewed: 2026-09-19
Double Glazing Cost Calculator US · UK
United States
USD · windows · The selected double-pane window style is the installed per-window baseline. Frame, glazing, full-frame replacement, and difficult access use isolated HomeCostNest percentage adjustments without adding a second full-window cost.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Casement | $0 | $0 | $0 | per windows |
| Double-hung | -$50 | -$100 | -$200 | per windows |
| Single-hung | -$150 | -$250 | -$500 | per windows |
| Sliding | -$100 | -$150 | -$300 | per windows |
| Picture | -$200 | -$250 | -$500 | per windows |
| Bay | $1,000 | $2,100 | $4,000 | per windows |
| Bow | $1,500 | $3,100 | $5,500 | per windows |
Adjustments / add-ons: Frame material, Glazing, Full-frame replacement, Difficult access / opening repair
HomeCostNest planning assumptions: Frame, glazing, installation, and access percentages are HomeCostNest planning assumptions. Permit requirements vary, especially when changing structural openings. Same-size replacement requirements should be confirmed locally.
Sources: HomeCostNest reviewed US V1 planning dataset · Last reviewed: 2026-09
United Kingdom
GBP · windows · Installed window style is the baseline; frame and glazing use modest HomeCostNest planning adjustments per window, while difficult access remains a separate project allowance.
| Benchmark | Low | Typical | High | Basis |
|---|---|---|---|---|
| Casement | £0 | £0 | £0 | per windows |
| Sash | £200 | £200 | £250 | per windows |
| Sliding | £100 | £100 | £150 | per windows |
| Tilt and turn | £100 | £100 | £150 | per windows |
| Bay | £600 | £1,500 | £2,750 | per windows |
| Bow | £1,000 | £2,000 | £3,750 | per windows |
Adjustments / add-ons: Frame material, Glazing, Difficult access or opening repair
HomeCostNest planning assumptions: Consider keeping a 10–15% contingency for unexpected work; it is not added automatically. Planning and compliance fees are not included.
Sources: Checkatrade Double Glazing Cost UK 2026 · Last reviewed: 2026-09-19
Assumptions, limitations, and verification
HomeCostNest labels planning assumptions where published data does not provide a precise adjustment. We avoid double-counting ordinary components already represented by an installed benchmark. National benchmarks cannot perfectly represent every city, contractor, property, specification, timing, or site condition.
Heat-pump and HVAC calculators estimate project cost; they do not replace professional equipment sizing. Structural projects may need professional building assessment. Permits, regulations, and final contractor pricing require a real project review.
Methodology review and updates
HomeCostNest may periodically review benchmark data, assumptions, methodology, source references, and market profiles. When data changes, calculator and transparency presentation should use the same underlying source.