# leaDCalc > DC power lead calculator for telephone central office power plants. (iPhone/iPad app by Vaughn Warriner.) - Source: https://appshunter.io/ios/app/leadcalc/id1487509498 (this page in markdown: same URL + `.md`) - Developer: [Vaughn Warriner](https://appshunter.io/developer/1487509497) - Category: Productivity, Utilities - Price: Free - Rating: 5.00/5 from 1 App Store ratings - Age rating: 4+ - Requires: iOS 16.0 · 157 MB - Languages: English - Released: 2019-11-12 - Data updated: 2026-06-21 - Monetization: free - User reviews in markdown: https://appshunter.io/ios/app/leadcalc/id1487509498/reviews.md ## What is leaDCalc? Application based on the Western Electric Co. Inc, Bell Laboratories, Bell System DC Power Lead Calculator which is in a circular slide rule format.   Using allowable voltage drops specifically designed for telephone company central office direct current power plants and distribution wiring. The application references 48 volt battery systems but also works for other direct current voltages such as 24 volt. When using for 24 volts or other, choose by the required loop voltage drop instead of the specific section of the circuit. Notes: 51. Voltage drop and wire size calculations are based on 2.00 volt LOOP drop from the power plant battery to the load equipment and return. 1.75 Final Volts Per Cell or 40 volts min. operating volts at the equipment for nominal 48V systems.
 (40 + 2 = 42 / 24 = 1.75fvpc) 

 52. LOOP length is used in the calculations, often the battery and returns are unequal length. The result VD is shown as ONE WAY.

 53. The formula used in the lead size calculations is:
CM = LoopLength * 11.1 * Fuse or Breaker @ 100% / VD
(T-Mobile does use 80% of the input breaker or fuse size to calculate DC power wires)
CM = LoopLength * 11.1 * Fuse or Breaker @ 80% / VD
For example the Bell System might use the leaDCalc recommended 66% of the input breaker or fuse size to calculate DC power wires. The Bell System terms Peak and Busy Hour are antiquated electro-mechanical switch central office terms so leaDCalc recommends using 66% of the input fuse or breaker size, ie. 600A fuse or breaker calculate using 400 amperes and which is exactly as was done at Western Electric Co., Inc. for Bell System Telephone offices. 54. BDFB is a Battery Distributing Fuse Board. Fuse Panel is rack mounted at or near the load equipment. Load Equipment is the actual device requiring power. 

 55. This application is intended for informational use. Based on the original Bell System Lead Calculator, Western Electric Co., Inc. Model GS-5420, 4-66.

 56. "leaDCalc" is NOT affiliated with any person or company or anything else anywhere. No how, no way. 
Especially NOT T-Mobile nor the Bell System or even Western Electric Co. Inc., all of whom are mentioned. 
This application is meant as a guide only in determining the size and or capacities of power wiring used in direct current (DC), charging and storage battery telephone systems. 
This application is NOT intended to decide what type of wire, (or if you should even use wire or busbars in your DC systems), no how, no way and it is not for use with alternating current (AC) systems. ## Key features - Circular slide rule format - Calculates allowable voltage drops - Determines DC power lead sizes - Supports 48V and 24V DC systems - References Bell System calculations ## Frequently asked questions about leaDCalc ### What is leaDCalc used for? leaDCalc is used to calculate direct current (DC) power lead sizes and allowable voltage drops specifically for telephone company central office power plants. It's based on the historical Western Electric Co. Inc. Bell System DC Power Lead Calculator. ### Does leaDCalc work with different DC voltages? Yes, leaDCalc references 48-volt battery systems but also works for other DC voltages such as 24 volts. When using for other voltages, you select by the required loop voltage drop rather than a specific circuit section. ### How does leaDCalc calculate wire size? The application uses a formula that considers loop length, fuse or breaker size (at a specified percentage, e.g., 66% or 80%), and the desired voltage drop (VD) to determine the required wire size in circular mils (CM). ### Is leaDCalc affiliated with T-Mobile or the Bell System? No, leaDCalc explicitly states it is NOT affiliated with any person, company, or entity, including T-Mobile or the Bell System. It is meant as an informational guide based on historical calculations. ### What is the voltage drop basis for leaDCalc? Voltage drop and wire size calculations are typically based on a 2.00-volt loop drop from the power plant battery to the load equipment and return. This aligns with 1.75 final volts per cell for nominal 48V systems. ### What does 'loop length' mean in leaDCalc? Loop length refers to the total length of the conductor path from the power source to the load and back. The application uses this value because battery and return paths are often of unequal length. ### Is leaDCalc suitable for AC systems? No, leaDCalc is strictly for direct current (DC) systems, including charging and storage battery telephone systems. It is not intended for use with alternating current (AC) systems. ### What is the update frequency for leaDCalc? The latest version, 26.1, was last updated on April 18, 2026. This indicates a very infrequent update cycle, with the last known update being in the future. ## Version history (last 5 releases) ### 26.1 — 2026-04-18 Version 26.1 Update new icon otherwise same old great power lead calculator. ### 5.1 — 2024-09-01 Version 5.1 Update for dark mode improvement, backwards compatibility for earlier devices & text spacing enhancement. ### 5.0 — 2024-08-15 Version 5.0 update for improved sizing for SE iPhone ### 4.0 — 2024-07-30 Version 4.0 Engineering calculation revision for specific target and minor upgrade, still the same great lead calculator. ### 3.0 — 2023-06-24 Minor improvements ## Apps similar to leaDCalc | App | Rating | Price | Category | | --- | --- | --- | --- | | [2017 Master Electrician Ref.](https://appshunter.io/ios/app/2017-master-electrician-ref/id1275949959) | 4.7 (1,181) | $9.99 | Productivity | | [Ugly's Electrical References](https://appshunter.io/ios/app/uglys-electrical-references/id1134770838) | 5.0 (1) | $12.99 | Productivity | | [kVA Calculator 2025](https://appshunter.io/ios/app/kva-calculator-2025/id6471555716) | — | $1.99 | Productivity | | [Electrical Formulator](https://appshunter.io/ios/app/electrical-formulator/id299749412) | 5.0 (1) | Free | Productivity | | [InductorCalc](https://appshunter.io/ios/app/inductorcalc/id1409402075) | — | $0.99 | Productivity | | [Fittings App ANSI](https://appshunter.io/ios/app/fittings-app-ansi/id1464409707) | 4.0 (5) | $3.99 | Productivity | ## More apps by Vaughn Warriner - [Passer Judge](https://appshunter.io/ios/app/passer-judge/id1492764082) - [DOGonEAT](https://appshunter.io/ios/app/dogoneat/id6449795344) All apps by Vaughn Warriner: https://appshunter.io/developer/1487509497 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-21.*