How Bilby works
Understanding your Bilby budget
What the total means
Your budget adds the work currently counted in your project. Low, expected and high are three planning scenarios. Expected is the model’s central scenario, not necessarily the midpoint. A total can exist while a required price is still missing; read the category status as well as the amount.
Count each scope once
Open a category and its line details to see the actual quantities, assumptions and receipt. A parent amount can contain several explanatory components. “Included” means the work belongs to a house, utility or other package; the component is not another charge. Optional work enters only when selected or applicable. Alternative municipal and private water arrangements are not added together. A saved legacy total may have less detail than a newly calculated estimate.
Prices, choices and your target
A target budget is a comparison amount; setting it does not make construction cheaper. Supply a real plot purchase price and house package price: Bilby does not invent these from national reference rates.
| Input | Unit | Where from? |
|---|---|---|
| Plot and house prices | SEK | Listing, supplier or your entry |
| Quantities and specifications | m², m, items | Planner geometry, project evidence or disclosed assumptions |
| Included and excluded work | scope | Supplier package and your choices |
| Target budget | SEK | Your planning limit |
From lines to total
For each scenario, Bilby sums the incremental amounts of counted lines, then adds active category subtotals. It preserves a usable project-specific estimate ahead of a national fallback. Your custom/manual price can replace the applicable estimate; it is not an extra estimate to add alongside it. An exact supplied amount can have the same low, expected and high values. Check the scope and inclusion setting before overriding a parent or a component, and use the reset/revert action when you want the automatic estimate again.
Illustrative budget
Suppose a fictional project has a plot at SEK 800,000, a house package at SEK 2,400,000 and separate groundworks of SEK 200,000 / 300,000 / 450,000. With only those three categories active, the totals are SEK 3,400,000 / 3,500,000 / 3,650,000. A SEK 100,000 drainage detail already owned by groundworks adds zero. Replacing groundworks with a scoped fixed quote of SEK 320,000 makes these three-category totals SEK 3,520,000 in every scenario. This is not a complete house-build budget.
Missing does not mean free
An entirely unavailable range stays unavailable. Where only some scenario values exist, Bilby fills missing values from the known values and keeps the order coherent. Pending and partial categories remain visible. Supplier inclusions, manual exclusions and unplanned work can reduce the counted total without reducing the physical work needed. Reconcile those choices before treating the result as funding required.
Method and review
Method reviewed 18 October 2026: project-budget calculation version 4 and the 2026 reference catalogue. The catalogue’s research date is 16 September 2026; today’s method review does not reverify every market price. Your actual quotations remain the evidence for your own contract. Read the related range guide before comparing totals from different assumptions.
The review date covers this explanation and its implemented method. Price and data dates are stated separately in the article.