Construction Material and Electrical Cost Calculation Formulas

This reference guide contains all the mathematical formulas used in the House Estimator application for calculating material requirements, electrical loads, energy consumption, electricity costs, and prepaid credit estimations.

Table of Contents

1. Tile and PVC Formulas

Basic Tile Properties

Area per piece (in square meters):

Area_per_piece = (Length_cm × Width_cm) ÷ 10,000

Note: Conversion from cm² to m² (1 m² = 10,000 cm²)

Room Area Calculation

Room_area = Room_length_m × Room_width_m × Room_quantity

Tile Requirements

Total pieces needed (with waste):

Total_pieces = ⌈(Room_area ÷ Area_per_piece) × (1 + Waste_percentage ÷ 100)⌉

Total boxes needed:

Total_boxes = ⌈Total_pieces ÷ Pieces_per_box⌉

Total cost:

Total_cost = Total_boxes × Price_per_box

Complete Tile Calculation Steps

Given:

  • Room_length (m), Room_width (m), Room_quantity
  • Tile_length (cm), Tile_width (cm)
  • Pieces_per_box, Price_per_box
  • Waste_percentage (default: 10%)

Calculate:

  1. Room_area = Room_length × Room_width × Room_quantity
  2. Area_per_piece = (Tile_length × Tile_width) ÷ 10,000
  3. Total_pieces = ⌈(Room_area ÷ Area_per_piece) × (1 + Waste_percentage ÷ 100)⌉
  4. Total_boxes = ⌈Total_pieces ÷ Pieces_per_box⌉
  5. Total_cost = Total_boxes × Price_per_box

2. Plywood Formulas

Basic Plywood Properties

Area per sheet (in square meters):

Area_per_sheet = Length_m × Width_m

Plywood Requirements

Total sheets needed (with waste):

Total_sheets = ⌈(Room_area ÷ Area_per_sheet) × (1 + Waste_percentage ÷ 100)⌉

Total cost:

Total_cost = Total_sheets × Price_per_sheet

Complete Plywood Calculation Steps

Given:

  • Room_length (m), Room_width (m), Room_quantity
  • Plywood_length (m), Plywood_width (m)
  • Price_per_sheet
  • Waste_percentage (default: 5%)

Calculate:

  1. Room_area = Room_length × Room_width × Room_quantity
  2. Area_per_sheet = Plywood_length × Plywood_width
  3. Total_sheets = ⌈(Room_area ÷ Area_per_sheet) × (1 + Waste_percentage ÷ 100)⌉
  4. Total_cost = Total_sheets × Price_per_sheet

3. Electrical Load Formulas

MCB (Miniature Circuit Breaker) Calculations

MCB Maximum Power (W):

MCB_power = MCB_amps × 230V × 1.0

Safe Operating Limit (80% of maximum) (W):

Safe_limit = MCB_amps × 230V × 0.8

Appliance Load Calculations

Total load per appliance (W):

Total_watts_appliance = Power_watt × Quantity

Total system load (W):

Total_system_watts = Σ(Total_watts_appliance) for all appliances

Safety check:

Within_limit = Total_system_watts ≤ Safe_limit

Energy Consumption Calculations

Daily energy consumption per appliance (kWh):

Daily_kWh_appliance = (Power_watt × Quantity × Hours_per_day) ÷ 1000

Monthly energy consumption per appliance (kWh):

Monthly_kWh_appliance = Daily_kWh_appliance × 30

Total daily system consumption (kWh):

Total_daily_kWh = Σ(Daily_kWh_appliance) for all appliances

Total monthly system consumption (kWh):

Total_monthly_kWh = Σ(Monthly_kWh_appliance) for all appliances

Electricity Cost Calculations

Daily cost per appliance:

Daily_cost_appliance = Daily_kWh_appliance × Rate_per_kWh

Monthly cost per appliance:

Monthly_cost_appliance = Monthly_kWh_appliance × Rate_per_kWh

Total daily system cost:

Total_daily_cost = Σ(Daily_cost_appliance) for all appliances

Total monthly system cost (including fixed charges):

Total_monthly_cost = Σ(Monthly_cost_appliance) + Fixed_monthly_charge

Prepaid Credit Calculations

Weekly cost:

Weekly_cost = Total_daily_cost × 7

Bi-weekly cost:

Biweekly_cost = Total_daily_cost × 14

Quarterly cost:

Quarterly_cost = Total_monthly_cost × 3

Credit duration calculation:

Duration_days = Credit_amount ÷ Total_daily_cost
Duration_hours = (Duration_days - ⌊Duration_days⌋) × 24

Weekly/Monthly duration estimates:

Duration_weeks = ⌊Duration_days ÷ 7⌋
Duration_months = ⌊Duration_days ÷ 30⌋

Complete Electrical Calculation Steps

Given:

  • MCB_amps (default: 6A)
  • Voltage = 230V (constant)
  • Rate_per_kWh (electricity tariff)
  • Fixed_monthly_charge (optional)
  • Appliances: [(Name, Power_watt, Quantity, Hours_per_day), ...]

Calculate:

  1. MCB_power = MCB_amps × 230 × 1.0
  2. Safe_limit = MCB_amps × 230 × 0.8
  3. For each appliance:
    • Total_watts_appliance = Power_watt × Quantity
    • Daily_kWh_appliance = (Power_watt × Quantity × Hours_per_day) ÷ 1000
    • Monthly_kWh_appliance = Daily_kWh_appliance × 30
    • Daily_cost_appliance = Daily_kWh_appliance × Rate_per_kWh
    • Monthly_cost_appliance = Monthly_kWh_appliance × Rate_per_kWh
  4. Total_system_watts = Σ(Total_watts_appliance)
  5. Total_daily_kWh = Σ(Daily_kWh_appliance)
  6. Total_monthly_kWh = Σ(Monthly_kWh_appliance)
  7. Total_daily_cost = Σ(Daily_cost_appliance)
  8. Total_monthly_cost = Σ(Monthly_cost_appliance) + Fixed_monthly_charge
  9. Within_limit = Total_system_watts ≤ Safe_limit
  10. Prepaid estimates:
    • Weekly_cost = Total_daily_cost × 7
    • Biweekly_cost = Total_daily_cost × 14
    • Quarterly_cost = Total_monthly_cost × 3

Practical Example

Example Calculation:

Given:

  • TV = 150W × 1 unit × 6 hours/day
  • LED Bulbs = 10W × 5 units × 8 hours/day
  • Refrigerator = 200W × 1 unit × 24 hours/day
  • Rate = $0.12/kWh
  • Fixed charge = $10/month

Calculations:

  • TV daily = (150 × 1 × 6) ÷ 1000 = 0.9 kWh
  • Bulbs daily = (10 × 5 × 8) ÷ 1000 = 0.4 kWh
  • Fridge daily = (200 × 1 × 24) ÷ 1000 = 4.8 kWh
  • Total daily = 6.1 kWh
  • Daily cost = 6.1 × $0.12 = $0.73
  • Monthly cost = (6.1 × 30 × $0.12) + $10 = $31.96
  • Weekly cost = $0.73 × 7 = $5.11

4. Energy Consumption Formulas

Daily energy consumption per appliance (kWh):

Daily_kWh_appliance = (Power_watt × Quantity × Hours_per_day) ÷ 1000

Monthly energy consumption per appliance (kWh):

Monthly_kWh_appliance = Daily_kWh_appliance × 30

Total daily system consumption (kWh):

Total_daily_kWh = Σ(Daily_kWh_appliance) for all appliances

Total monthly system consumption (kWh):

Total_monthly_kWh = Σ(Monthly_kWh_appliance) for all appliances

5. Electricity Cost Formulas

Electricity Cost Calculations

Daily cost per appliance:

Daily_cost_appliance = Daily_kWh_appliance × Rate_per_kWh

Monthly cost per appliance:

Monthly_cost_appliance = Monthly_kWh_appliance × Rate_per_kWh

Total daily system cost:

Total_daily_cost = Σ(Daily_cost_appliance) for all appliances

Total monthly system cost (including fixed charges):

Total_monthly_cost = Σ(Monthly_cost_appliance) + Fixed_monthly_charge

6. Prepaid Credit Estimator Formulas

Prepaid Credit Calculations

Weekly cost:

Weekly_cost = Total_daily_cost × 7

Bi-weekly cost:

Biweekly_cost = Total_daily_cost × 14

Quarterly cost:

Quarterly_cost = Total_monthly_cost × 3

Credit duration calculation:

Duration_days = Credit_amount ÷ Total_daily_cost
Duration_hours = (Duration_days - ⌊Duration_days⌋) × 24

Weekly/Monthly duration estimates:

Duration_weeks = ⌊Duration_days ÷ 7⌋
Duration_months = ⌊Duration_days ÷ 30⌋

7. Project Summary Calculations

Material Type Aggregations

Plywood totals:

Total_plywood_sheets = Σ(Total_sheets) for all plywood calculations
Total_plywood_cost = Σ(Total_cost) for all plywood calculations

Tile totals:

Total_tile_boxes = Σ(Total_boxes) for all tile calculations where type = 'tile'
Total_tile_cost = Σ(Total_cost) for all tile calculations where type = 'tile'

PVC totals:

Total_pvc_boxes = Σ(Total_boxes) for all tile calculations where type = 'pvc'
Total_pvc_cost = Σ(Total_cost) for all tile calculations where type = 'pvc'

Project total cost:

Total_project_cost = Total_plywood_cost + Total_tile_cost + Total_pvc_cost

8. Key Constants and Defaults

Parameter Default Value Unit Description
Tile waste percentage 10% Percentage Default waste for tile cutting and breakage
Plywood waste percentage 5% Percentage Default waste for plywood cutting
Electrical voltage (V) 230V Volts (V) Standard household voltage
MCB default rating 6A Amperes (A) Default circuit breaker rating
Safety factor (80%) 0.8 Decimal (80%) Safety derating for electrical loads
Power factor (100%) 1.0 Decimal (100%) Resistive load power factor
Default electricity tariff $0.12 $/kWh Default rate per kilowatt-hour
Monthly calculation period 30 Days Standard month duration for calculations
Weekly calculation period 7 Days Standard week duration
Quarterly calculation period 3 Months Standard quarter duration
kWh conversion factor 1000 W/kW Watts to kilowatts conversion
Default appliance usage 8 Hours/day Default daily usage hours

6. Mathematical Functions Used

  • Ceiling function ⌈x⌉: Always rounds up to the next integer
    • Example: ⌈2.1⌉ = 3, ⌈2.0⌉ = 2
  • Summation Σ: Adds all values in a series or represent the sum of a series of values
  • Area conversion: 1 m² = 10,000 cm²

9. Validation Rules

  1. All dimensions must be positive values (> 0)
  2. Waste percentage must be between 0% and 100%
  3. Quantities must be positive integers (≥ 1)
  4. Prices must be positive values (≥ 0)
  5. Electrical power ratings must be positive values (> 0)
  6. MCB ratings must be standard values (typically 6A, 10A, 16A, 20A, 32A, etc.)
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