BS EN Certified Calculators

Built for UK TradesNot Guesswork

Professional calculators for Gas Safe engineers, electricians, plumbers and builders. Generate CP12, G3, EICR and OFTEC certificates in seconds.

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✓ Works offline (PWA)
gas / pipe-sizing
🔥 Gas
⚡ Electrical
🔧 Plumbing
Gas Rate
2.83m³/h
Pipe Length
12.5metres
✓ Recommended Size
22mm
Velocity 4.2 m/s · ΔP 0.8 mbar — BS 6891 compliant
✓ COMPLIANT
// BS 6891:2015 Gas Installation
// BS 7671:2018+A2:2022 IET Wiring
// Building Regs Part G3
// BS EN 806-3:2006 Plumbing
// OFTEC TB3 Oil Systems
// BS 8500-1:2015 Concrete
// BS 5268-2:2002 Timber
// ACOP L8 Legionella
// Building Regs Part L 2021
// BS EN 12056-3 Drainage
// Gas Safe Register Compliant
// NICEIC / NAPIT Approved Format
// BS 6891:2015 Gas Installation
// BS 7671:2018+A2:2022 IET Wiring
// Building Regs Part G3
// BS EN 806-3:2006 Plumbing
// OFTEC TB3 Oil Systems
// BS 8500-1:2015 Concrete
// BS 5268-2:2002 Timber
// ACOP L8 Legionella
// Building Regs Part L 2021
// BS EN 12056-3 Drainage
// Gas Safe Register Compliant
// NICEIC / NAPIT Approved Format
// 5 professional modules

Every Trade.
One Platform.

From gas pipe sizing to U-value calculations — every calculator built to the exact British Standard your job requires.

🔥
Gas Engineering
20+ calculators covering pipe sizing, heat loss, boiler output, flue design and more. Full CP12 suite.
BS 6891CP12Gas Safe20+ calcs
⚡
Electrical
Cable sizing, voltage drop, max demand, RCD protection, EV charger load and full certification suite.
BS 7671EICR18th Edition13 calcs
🛢️
Oil / OFTEC
Oil pipe and tank sizing, flue design, consumption analysis and OFTEC CD/11 commissioning certificates.
OFTEC TB3BS 5410CD/11
🔧
Plumbing
Pipe sizing, G3 unvented commissioning, hot water cylinder sizing, Legionella risk assessments.
BS EN 806G3ACOP L8
🏗️
Construction
Concrete mixes, U-values, timber spans, drainage design, material estimating and staircase calculations.
BS 8500Part LBS 5268
📊
Project Manager
Organise jobs by customer and postcode. Save calculations to projects. Export full PDF reports.
Postcode lookupPDF exportHistory
// why tradespeople choose us

The Tools You
Actually Need

📄
Professional PDF Certificates
Generate CP12, G3, EICR, Minor Works and OFTEC certificates with your logo, Gas Safe number and digital signature. Send directly to landlords by email.
✅
British Standards Built-In
Every calculation references the exact BS EN standard. Compliance check on every result — green tick or red warning, no guessing.
📱
Works Offline on Any Device
Install as a PWA on your phone, tablet or laptop. Calculate on site with no signal. Auto-syncs when you're back online.
🗂️
Job History & Projects
Every calculation saved automatically. Search by customer, address or postcode. Duplicate previous jobs to save time on repeat installations.
📮
Send Certificates by Email
Generate a certificate and send it directly to your customer or landlord from the app. No downloading, no attaching — one tap.
🔔
CP12 Expiry Reminders
Track all your CP12 certificates with expiry dates. Get reminders 30 days and 7 days before renewal — never miss a landlord cert again.
// simple pricing

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£0 / month
  • →All 60+ calculators — unlimited use
  • →BS EN compliance checks on every result
  • →3 trial PDFs across all calculators
  • →1 saved project
  • →Unlimited PDF exports
  • →All certificates (CP12, G3, EICR, OFTEC)
  • →Email sending
  • →CP12 expiry tracker
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£5.99 / month
  • →Everything in Free
  • →Unlimited PDF exports — no watermark
  • →All certificates (CP12, G3, EICR, OFTEC)
  • →Send certificates by email
  • →Unlimited projects & history
  • →CP12 expiry tracker + reminders
  • →Priority support
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