Net Effective Rent (NER)
NER normalizes a lease's true monthly cost by spreading concessions across the full term. A 12-month lease at $4,500/mo with 2 free months → NER = ($4,500 × 10) ÷ 12 = $3,750/mo.
Formula Concepts
Quick-reference formulas, examples, and calculator links for common finance, engineering, real estate, education, and health calculations.
Formula Concepts overview
This standalone page summarizes the most useful swervice resources for this topic and links visitors to the related calculator tools, formula explanations, and support pages.
Thrust-to-Weight Ratio (TWR)
TWR measures if a propulsion system can overcome gravity. Above 1.0 = can lift vertically. The Saturn V launched at just 1.18:1 — increasing as propellant burned off.
Dynamic Compression Ratio (DCR)
A high-duration cam closing at 70° ABDC can drop DCR from 11.0:1 static to 7.8:1 dynamic. Safe DCR for 93-octane on aluminum heads is typically 8.0–8.5:1.
Surface Speed: RPM to FPM
Surface feet per minute governs heat and tool wear — not RPM alone. A 2-inch end mill at 1,000 RPM runs at 524 FPM. HSS in mild steel: target 80–130 SFPM.
Fix-and-Flip: The 70% Rule
The 70% rule reserves 10% for holding/selling costs, 10% for the purchase discount, 10% as profit. ARV $280k, rehab $45k → max offer = $151k.
Paver Base Compaction Factor
Crushed stone compacts 15–20% from delivered volume. For 200 sq ft needing 6" compacted base: order ~4.7 cu yd. ICPI: minimum 4" for pedestrian, 6–8" in freeze-thaw zones.
German Grade Conversion
Modified Bavarian formula converts to German 1–5 scale (1.0 = best). For 85% where Nmax=100, Nmin=50: GG = 1 + 3 × (100−85) ÷ (100−50) = 1.9 (gut).
Rucking Calorie Burn (MET)
MET for rucking: 4.3 (unloaded) to 8.5+ (heavy load, steep terrain). 85 kg person at MET 6.5 = 552 kcal/hr. Add 25–35% for 5% incline grades.