U-Monkey —
U-value Calculator
Build up any wall, roof or floor and get its U-value live, to BS EN ISO 6946 and BR 443 — with a self-drawing cross-section, Part L and Future Homes Standard checks, a condensation screening, thermal mass and decrement factor to ISO 13786, and 250+ real UK products. Completely free, including the PDF.
Check a U-value →WaterMonkey — Part G Water Calculator
Part G water efficiency calcs to the official methodology — watch PASS/FAIL flip live at 125 or 110 l/p/d as you type, rainwater & greywater included. PDF reports for Building Control submission from £25 +VAT (£30 inc VAT).
Run a Part G calc →NutrientMonkey — Nutrient Neutrality Calculator
Nutrient budgets for new dwellings across all 27 Natural England catchments — nitrogen and phosphorus, NE methodology with the 20% buffer, live in your browser. Planning-ready reports £79 +VAT (£94.80 inc VAT).
Work out a nutrient budget →SoakMonkey — Soakaway Calculator
Size a soakaway to BRE Digest 365 — percolation test analysis, FSR rainfall, four construction types and a climate-change uplift, all in your browser. Building Control-ready reports £25 +VAT (£30 inc VAT).
Size a soakaway →ΨMonkey — Psi Value Calculator
Work out junction Ψ-values and f_Rsi temperature factors to BS EN ISO 10211, free in your browser — no sign-up, no spreadsheet gymnastics. Stamped PDF reports for Building Control submission from £35 +VAT (£42 inc VAT).
Model a junction → NewGlazeMonkey — Part L Extension Calculator
Over-glazed extension? The 25% allowance, every element against Table 4.2 and the area-weighted U-value comparison with the notional extension, live as you type — plus conservatory exemption and Table 4.3 renovation checks. Building Control-ready reports £35 +VAT (£42 inc VAT).
Check an extension → NewRenoMonkey — Part L Renovation Calculator
Re-roofing, re-rendering, dry-lining, cavity fill, a garage or loft conversion? The 50% renovation trigger, Table 4.3 threshold and improved U-values, the 15-year payback test and controlled fittings — the same engine as GlazeMonkey, led from the renovation end. Building Control-ready reports £35 +VAT (£42 inc VAT).
Check a renovation → NewGridMonkey — Live Grid Mix
Where Britain's electricity is coming from right now — the live generation mix as one big pie, with carbon intensity, demand and interconnector flows. Group it by fuel, company, power station or wind farm. Free, no sign-up.
See the grid live → NewTreeMonkey — Carbon Translator
What does a tonne of CO₂ actually look like? Turn any amount of carbon — or your own project — into trees, car miles, flights and homes, with a scannable share card. Free forever, no sign-up.
Translate a tonne of CO₂ →More Monkeys on the way
The Collection is growing — we're building more calculators for assessors and designers. Got one that would save you a headache? Tell us.
Suggest a tool →Some of it there is no calculator for
A Monkey will run any calculation with a published method and a deterministic answer. The work that needs an accredited assessor is a different matter — a new dwelling's SAP calculations and EPC, an SBEM model for a commercial building, air tightness or sound testing on site, or a planning energy statement. We do those too, as a consultancy, and have since long before the calculators existed.
Every calculator is free. The subscription is about the paperwork.
You never pay to get an answer out of a Monkey. You pay only when you need that answer written up as a Building Control submission PDF — and a subscription is optional. Here is exactly what one changes.
Free
£0
- Every tool, in full. No account, no limits, no trial that runs out.
- Reports carry the Energycount logo.
- Buy any report one-off when you need one.
Monkey Pro
£10/month +VAT
or £100/year +VAT
- Your practice on every report instead of ours — your logo, practice name, address and contact on the header, and your project, client and revision references on the page.
- From every tool, on one plan.
- Report prices unchanged — Pro is the branding, not a discount.
Monkey Pro Unlimited
£49/month +VAT
or £490/year +VAT
- Everything in Pro.
- Thermal bridge and condensation reports included outright — export as many as your projects need, no per-report charge — plus the multi-junction schedule.
- Worth it from two thermal bridge or condensation reports a month.
Not included in either plan: soakaway (£25 +VAT), nutrient neutrality (£79 +VAT), Part G water (£25 +VAT, plus £15 per extra dwelling type) and the Part L extension and renovation reports (£35 +VAT) are one-off purchases on every plan. Your branding still applies to them. No subscription changes a calculation, and report IDs verify the same either way.
After the number rather than the calculation? The building regulations reference has the Part L, Part O, Part G, Part E and SAP figures these tools work to, on one dated page.