Our Methodology

Phone depreciation follows a predictable curve that varies by brand tier:

• Premium brands (Apple, Samsung Galaxy S/Z): ~70% value after year 1, declining ~15% per year
• Mid-tier brands (Google Pixel, OnePlus): ~55% after year 1, declining ~18% per year
• Budget brands: ~40% after year 1, declining ~20% per year

Condition adjustments range from +5% (Like New) to -25% (Poor). These curves are derived from analyzing trade-in offers from major retailers and resale platforms.

Lithium-ion batteries degrade based on charge cycles and age:

• Cycle life: Most laptop batteries are rated for 300-500 full cycles before reaching 80% capacity
• Calendar aging: Batteries lose ~2-3% capacity per year even when unused
• Temperature impact: Heat accelerates degradation significantly

We estimate remaining capacity using the formula: Current Capacity = Original × (1 - (cycles/rated_cycles) × 0.2) × age_factor

USB-C Power Delivery compatibility is determined by wattage and protocol support:

• Wattage matching: Charger must meet or exceed device requirements
• Protocol support: PD 3.0, PPS, QC compatibility varies by device
• Voltage/amperage: Must match supported profiles (5V/9V/15V/20V)

We cross-reference device power requirements with charger specifications to determine compatibility and charging speed.

Power supply requirements are calculated from component TDP and efficiency:

• GPU TDP: Sourced from manufacturer specifications
• System overhead: CPU, RAM, storage, fans typically add 100-200W
• Headroom: We recommend 20-30% overhead for efficiency and transient spikes
• 12V rail: Modern GPUs draw primarily from the 12V rail; we verify adequate amperage

Formula: Recommended PSU = (GPU TDP + System Power) × 1.25

Pixels Per Inch (PPI) is calculated using the Pythagorean theorem:

• Diagonal pixels: √(width² + height²)
• PPI: Diagonal pixels ÷ screen diagonal in inches
• Clarity rating: Based on typical viewing distances (24" at arm's length)

We rate sharpness as: Retina-class (>200 PPI), Sharp (150-200), Adequate (100-150), Noticeable pixels (<100).

Optimal viewing distance is based on resolution and field of view:

• THX recommendation: 40° field of view for cinema experience
• SMPTE standard: 30° field of view for comfortable viewing
• Resolution factor: 4K allows closer viewing without visible pixels

General guidelines: Distance = Screen size × 1.2 (immersive) to × 1.6 (comfortable) for 4K. For 1080p, multiply by 1.5 to 2.5.

Storage lifespan depends on technology and usage patterns:

• SSDs: Rated in TBW (Terabytes Written); consumer drives typically 150-600 TBW
• HDDs: MTBF ratings of 1-2 million hours; practical life 3-5 years for consumer drives
• Flash storage: Limited write cycles; we estimate based on daily write volume

We calculate remaining lifespan using: Years Left = (TBW Rating - Current Writes) ÷ (Daily Writes × 365)

Bandwidth requirements are calculated from simultaneous usage:

• 4K streaming: 25 Mbps per stream (Netflix recommendation)
• 1080p streaming: 5-10 Mbps per stream
• Video calls: 3-5 Mbps per participant
• Gaming: 10-25 Mbps (latency matters more than bandwidth)
• General browsing: 1-5 Mbps per device

We sum all activities and add 20% overhead for background tasks and network efficiency.

Real-world battery life is estimated from capacity, screen size, and usage profile:

• Base calculation: Battery capacity (Wh) ÷ estimated power draw
• Screen size factor: Larger screens draw more power (13" ~8W, 15" ~12W, 17" ~15W base)
• Brightness impact: Each 10% brightness adds ~5-8% power draw
• Usage profiles: Light (0.7x), Normal (1.0x), Heavy (1.4x), Gaming (2.0x) multipliers

Formula: Hours = Capacity ÷ (Base Draw × Screen Factor × Brightness Factor × Usage Multiplier)

RAM recommendations are calculated by summing typical memory usage per application category:

• OS baseline: Windows ~4GB, macOS ~3GB idle
• Browser tabs: ~150-300MB per tab (varies by content)
• Creative apps: Photoshop 4-8GB, Video editing 8-16GB, 3D rendering 16-32GB
• Development: IDEs 2-4GB, Docker containers 2-8GB, VMs 4-16GB each
• Gaming: Modern games 8-16GB, plus OS overhead

We add 25% headroom and round up to the nearest standard RAM configuration (8/16/32/64GB).

Transfer time is calculated from theoretical speeds adjusted for real-world overhead:

• USB 2.0: 480 Mbps theoretical, ~35 MB/s practical
• USB 3.0: 5 Gbps theoretical, ~400 MB/s practical
• USB 3.2 Gen 2: 10 Gbps theoretical, ~800 MB/s practical
• Thunderbolt 3/4: 40 Gbps theoretical, ~2,800 MB/s practical
• Network: Advertised speed × 0.85-0.90 efficiency factor

Formula: Time = File Size ÷ (Theoretical Speed × Efficiency Factor)

Cloud storage costs are compared using current pricing tiers from major providers:

• iCloud: 50GB/$0.99, 200GB/$2.99, 2TB/$10.99/month
• Google One: 100GB/$1.99, 200GB/$2.99, 2TB/$9.99/month
• OneDrive: 100GB/$1.99, Microsoft 365 includes 1TB at $6.99/month
• Dropbox: Plus 2TB/$11.99, Professional 3TB/$19.99/month

We calculate annual costs and cost-per-GB to help identify the best value for your storage needs. Prices may vary by region.

Data consumption is calculated from bitrates used by major streaming services:

• Video (Netflix/YouTube): SD ~1GB/hr, HD ~3GB/hr, 4K ~7GB/hr
• Music (Spotify/Apple Music): Normal ~70MB/hr, High ~150MB/hr, Lossless ~600MB/hr
• Video calls: Audio only ~40MB/hr, Video ~270MB/hr, HD Video ~1.5GB/hr
• Gaming: 40-150MB/hr depending on game type (downloads separate)

Formula: Monthly Usage = Σ(Hours per activity × Data rate per hour)

Throw distance is calculated using throw ratio and screen dimensions:

• Throw ratio: Distance to screen ÷ screen width
• UST projectors: 0.2-0.4 throw ratio
• Short throw: 0.4-0.8 throw ratio
• Standard: 1.2-2.0 throw ratio
• Long throw: 2.0+ throw ratio

Formula: Distance = Screen Width × Throw Ratio or Screen Width = Distance ÷ Throw Ratio

Screen width is derived from diagonal using aspect ratio (16:9, 16:10, etc.).

Amplification requirements are calculated from headphone impedance and sensitivity:

• Power required: Based on target SPL (typically 110dB peak) and sensitivity
• Voltage required: V = √(P × Z) where P is power in watts, Z is impedance
• Damping factor: Headphone impedance ÷ source output impedance (8:1 minimum recommended)
• Source capabilities: Phones ~1V, laptops ~1-2V, dedicated DACs/amps ~2-7V

Formula: Power (mW) = (10^((Target dB - Sensitivity) / 10))

System power is calculated by summing component TDPs with efficiency factors:

• CPU TDP: From manufacturer specs (65W-250W typical)
• GPU TDP: From manufacturer specs (75W-450W typical)
• RAM: ~3-5W per stick
• Storage: SSD ~2-5W, HDD ~6-10W
• Motherboard/fans: ~30-50W overhead

Formula: Recommended PSU = Total TDP × 1.25 (for 80% load efficiency)

We recommend 80+ rated PSUs and account for transient power spikes on modern GPUs.

Charging time accounts for the non-linear charging curve of lithium batteries:

• 0-50%: Fast charging at maximum supported wattage
• 50-80%: Reduced speed (~70% of max) to manage heat
• 80-100%: Trickle charging (~30% of max) to protect battery longevity
• Charger matching: Device charges at the lower of charger output or device max input

Formula: Time = Σ(Capacity per phase ÷ Effective charging rate per phase)

Bluetooth range is estimated from version, environment, and device factors:

• Bluetooth 4.x: ~30-35 feet typical, 60 feet max
• Bluetooth 5.x: ~40-60 feet typical, 240 feet max (4x improvement)
• Environment factors: Walls reduce range 25-75%, interference 20-40%
• Codec impact: High-bitrate codecs (LDAC, aptX HD) reduce effective range 10-20%
• Device quality: Premium earbuds have better antennas (+10-20% range)

Formula: Range = Base Range × Environment Factor × Codec Factor × Quality Factor

Display scaling affects effective resolution and perceived sharpness:

• Native PPI: √(width² + height²) ÷ diagonal inches
• Effective resolution: Native resolution ÷ scaling factor
• Effective PPI: Native PPI ÷ scaling factor (determines UI density)
• Integer scaling: 100%, 200%, 300% provide pixel-perfect rendering
• Non-integer scaling: 125%, 150%, 175% may cause slight blur in some apps

We recommend: <100 PPI = 100%, 100-150 PPI = 125%, 150-200 PPI = 150-200%, >200 PPI = 200%+

Device value depreciation follows category-specific curves:

• iPhones: ~30% year 1, then ~15%/year (retain value longest)
• Android flagships: ~40% year 1, then ~20%/year
• MacBooks: ~20-25% year 1, then ~12%/year
• Windows laptops: ~35-45% year 1, then ~18-22%/year
• Condition adjustment: Mint (100%), Excellent (92%), Good (82%), Fair (65%), Poor (45%)

Formula: Value = Original Price × Age Factor × Condition Multiplier

Age factor uses exponential decay with device-specific rates derived from resale market analysis.