VoltPrep Electrician Exam Prep
Exam prep1,000 practice questions for the journeyman and master electrician exams, with the code-based reasoning behind each answer.
Field tools for the trades. Apps for learning. Games worth replaying.
TapForge Studios is a one-person Android studio in Crown Point, Indiana. Field toolkits and certification prep for the trades, K-8 learning apps, and games worth replaying — all offline-first, all built by hand.
- 59 Android apps
- 43 free calculators
- 51 state paycheck pages
- 9 sample exams
Find your app
All 59 appsEverything is on Google Play, most of it works offline, and none of it asks you to make an account.
Games
Arcade, puzzle and card games built for one more run.
15 apps →Learning
The Mathlings math apps for kids, typing, languages, the U.S. citizenship test and more. Ad-free and offline.
13 apps →Trades & Certification
Field toolkits and exam prep for the trades: fire alarm, sprinkler, electrical, HVAC, plumbing, inspection and welding.
18 apps →Everyday Tools
Scanners, planners, trackers, calculators and money tools for every day.
13 apps →
For kids · Pre-K to algebra
Meet the Mathlings
8 friendly math apps: lessons, quizzes, telling time and money, times tables, fractions, decimals, geometry and algebra. No ads, no accounts, and they work offline.
Teacher Approved 4 are Teacher Approved on Google Play
Apps for the trades
All 59 appsField toolkits and full-length mock exams that work with no signal. Built by a tradesman, on Google Play.
CoreForge: HVAC Exam Prep
Exam prepHVAC certification exam prep: 1,000 questions and mock exams, fully offline.
Fire Alarm Prep: NICET Exam
Exam prepNICET fire alarm exam prep: 1,000 questions, mock exams and flashcards.
Fire Sprinkler ITM Prep: NICET
Exam prepNFPA 25 inspection, testing and maintenance prep with real-length NICET mock exams.
Voltbox: Electrician Toolbox
Field toolkitWire, breaker and conduit calculators plus a full multimeter guide, all offline, so they work in a basement or a mechanical room with no signal.
Airforge: HVAC/R Field Tools
Field toolkit33 offline HVAC/R tools: P/T charts, superheat, subcooling and diagnosis, ready on the rooftop.
Fireforge: Fire Alarm Tools
Field toolkitNAC drop, battery, candela and conduit bending: the fire alarm tech's toolkit, offline.
Pipeforge: Plumbing Tools
Field toolkitPipe sizing, DWV, gas, water heater and well calculators, plus offline fault-finding.
Free calculators
All 43 calculatorsNo sign-up. Each one shows its formula and a worked example, and the apps do the same math offline.
Pay & taxes 6
Electrical 10
HVAC / refrigeration 8
Plumbing & piping 3
Fire protection 6
Construction 5
Trucking 2
Rental property & mortgages 3
- Take-Home Pay Calculator: All 50 States + DC (2026)Pay & taxesYour paycheck after federal, state and payroll taxes. Every state and DC, 2026 tax rules.
- Voltage Drop CalculatorElectricalPercent voltage drop for any wire size and run length, plus the smallest wire that passes.
- Wire Size Calculator (NEC Ampacity)ElectricalWire size and breaker from load amps, with continuous-load and derating.
- Superheat and Subcooling CalculatorHVAC / refrigerationSuperheat and subcooling from your gauge pressures and line temperatures, with target superheat.
- Fire Alarm Battery Calculator (NFPA 72)Fire protectionRequired amp-hours for 24 or 60 hours of standby plus alarm, with the 20% margin.
- Overtime Pay Calculator (Time and a Half, Double Time)Pay & taxesWeekly and yearly gross with overtime, the blended hourly rate, and a 0 to 20 OT-hour table.
Free practice questions
All practice questionsSample questions with the reasoning behind every answer, and a new one each day. The full question banks and timed mock exams are in the apps.
How-to guides
- How Much Concrete Do I Need? Slabs, Footings and PiersConstruction · 5 min read
- How Overtime Pay Is Calculated (and When You Are Owed It)Pay & taxes · 5 min read
- How to Apply the NEC 3% Voltage Drop RuleElectrical · 5 min read
- How to Calculate Cash-on-Cash Return on a Rental PropertyRental property & mortgages · 4 min read
In-depth guides
- How to become a U.S. resident and citizenGuide · Español
- Mathlings: math apps for kids, Pre-K to algebraGuide · Español
- NICET certification: levels, exams, how to passGuide
Free, with no ads, made by one person
Every calculator, practice question and guide here is free to use. If something on this site saved you time, you can help keep it that way.