Coverage Score Calculator: Gold, Silver or Bronze After the Night Walk

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Opens on the book's plan, before the night walk: the doorbell's own figures and the book's predictions. Walk your routes after dark, then enter what you found.

Gold and Silver: the door and the approach routes (the night walk)

Doorbell pixels wide

Its view degrees

A caller stands m away

Or: pixels across a face counted on a night still

Approach routes walked

Blind spots found on the night walk

Of them fixed

Cameras planned

Cameras installed blank = as planned

Bronze: the plan drawn, and the predictions measured (within 10%)

The plan is drawn to scale

Front wall length m, predicted

Measured m

Drive area m², predicted

Measured m²

Eaves height m, predicted

Measured m

Tree height m, predicted

Measured m

The quote level (optional): your estimate within 15% of a real quote, or your DIY bill under it

Your estimate

A real quote

Your DIY bill

Enter the door's camera and the night walk, then press Calculate.

The formula

Density at the door = pixels ÷ (2 × distance × tan(view ÷ 2)), or the pixels across a face ÷ 0.16 m
Gold: identify (250 px/m) at the door, no blind spot found on the approach routes, and the cameras you planned
Silver: recognize (125 px/m) at the door, and every blind spot found has been fixed
Bronze: the plan drawn to scale, and every measurement within 10% of your prediction: gap = |measured − predicted| ÷ measured (5% scores 3 points, 10% 2, 20% 1)
Quote level: |quote − estimate| ÷ quote within 15%, or the DIY bill under the quote

The book's worked example, Chapter 11. The book's doorbell, 1,920 px and 140°, puts 349.4 px/m on a caller 1.0 m away: identify. The final plan, 5 cameras and the doorbell, leaves no blind stretch on the 4 approach routes, so on paper it is Gold. The predictions to measure for Bronze: front wall length 10 m, drive area 49 m², eaves height 5.4 m, tree height 13.75 m. The quote level: our estimate 2,485.59 is 10.6% under the 2,780.00 quote, and the DIY bill 1,357.80 is under it.

Check it. Walk every route at night with a friend while someone watches the live view: count the steps nobody sees. A level is only as good as that walk.

Honest limits. A level is a record of how well the plan matched your home, not a rating of how safe it is. Coverage is a plan, not a promise: cameras and lights are one layer among locks, neighbors and habits. The book's house was worked out on paper from published figures, not surveyed by us: measure your own, and walk your own plot at night. Prices are illustrative US prices from November 2026, shown without a currency sign; put in your own. Everything stays in your browser: no sign-up, nothing stored.

These calculators go with Every Angle (Make It Add Up, Book 2), where every number on this page is worked by hand.