Stinger Pro Tools

ELECTRICAL OPS, INC.

About this app

Plan a 400-foot pull and watch the app draw the run, bend by bend, with the tension and sidewall pressure at every elbow and a warning before your cables jam. Size a pull box and get the knockout layout for every wall, dimensioned for the crew to punch. Size a transformer and get the one-line drawing, with every conductor, breaker and bonding jumper labeled.

Stinger Pro Tools was built by a master electrician with 40 years in the trade. Every answer shows the inputs, the math step by step, the NEC sections it rests on, and a drawing of exactly what was calculated. Share any result as a clean PDF you can hand to a GC, an engineer or an inspector.

PULL TENSION PLANNER
• Lay out the run as you'd walk it: up 30 ft, 90° left, 150 ft level, a 30° kick, down into the gear
• Tension at every bend, peak sidewall pressure against the cable maker's limit, and which end to pull from
• Jam ratio checked, with a to-scale cross-section of the cables in the conduit
• THHN and XHHW-2 weights from the manufacturer's data, lubricant friction built in

PULL BOXES AND KNOCKOUTS
• Pull box sizing for straight, angle and U pulls
• Knockout layouts for every wall, with real hole-saw sizes
• Knockout Layout tool: put your conduits in your order and get every hole center from the edges, with room for Myers hubs, grounding-bushing lug swing and the puller's coupler. Every gap is labeled with the rule that set it

CONDUIT, WIREWAY AND FEEDERS
• Conduit fill drawn to scale, conductors in their real system colors
• Wireway fill with the 20% and splice rules
• Feeder sizing: ambient correction, rooftop runs, more than three current-carrying conductors, parallel sets, the 10 ft rule, and voltage drop by Chapter 9 Table 9, drawn as one vertical diagram

TRANSFORMERS, SERVICES AND TAPS
• Transformer sizing with primary and secondary protection, secondary conductor rules, bonding jumpers and GEC on a one-line drawing
• Service sizing: conductors, the main, ground-fault protection when it's required, main bonding jumper and GEC
• Feeder taps: the 10 ft, 25 ft and outside rules, every condition checked. If a tap fails, it tells you why and what to change

MOTORS, GENERATORS AND FIRE PUMPS
• Motor circuits drawn from breaker to overloads
• Generators: conductor sizing, and 3-pole versus 4-pole transfer switch bonding, drawn
• Fire pumps: the one circuit built backwards on purpose. Locked-rotor protection, no overloads, and the voltage drop limits that are code here

GROUNDING AND BONDING
• Answer a few questions about the service and electrodes, and get the GEC to each one, jumper sizes, ground rod rules, and a drawing of the whole system
• A common-violations list, including aluminum GECs too close to the earth

MORE TOOLS
• Fault current, duct banks and wire-bending space

CODE FINDER AND CODE REFERENCE
• Type what you're working on ("ground rod," "outside tap," "Ufer") and get the sections to read. 180 topics, trade words welcome, misspellings forgiven
• Full tables, including Chapter 9 Tables 8 and 9, knockout and bushing dimensions, and illustrated entries
• A guide to what's new in the 2026 NEC
• Field Testing & Safety: megger testing with an isolation checklist, ground resistance testing, test before touch

BUILT FOR THE FIELD
• Works offline: no signal needed in the basement or the pump station
• Save jobs and reopen them later; share results as PDFs
• For systems 600 V and below

YOURS TO KEEP
Pay once and it's yours. No ads, no subscription, no account. Your jobs stay on your phone, and nothing you enter is collected, sold or shared.

MADE FOR PROFESSIONALS
For electricians, contractors and estimators who know the work and want it done faster. Every result shows its math and its code sections, so you can check it at a glance.

What’s new

Corrections and improvements:
- Parallel feeders and motors: each raceway now gets a full-size equipment grounding conductor sized from the breaker rating.
- Clearer wording throughout, with American spelling.
- Conduit Fill no longer suggests a size that can jam.
- Fixes for Pull Tension, Pull Box, Wireway, Knockout Layout and Service.
- You now set the voltage drop you'll accept.