What is a roof pitch guide card, and how do you use one?
Short answer. A roof pitch guide card is a pocket card, often clear plastic, printed with angled lines labeled 3/12, 4/12, 6/12 and so on. Stand square to a gable end, hold the card at arm's length with its bottom edge level, and match the roof's rake edge to the closest line; it gets you within about one pitch without climbing.
How to use the card
- Find a gable end you can see straight on. Standing off to the side distorts the angle and makes the roof look flatter or steeper than it is.
- Back up until the whole rake edge fits in view.
- Hold the card at arm's length. Keep its bottom edge level, using the built in bubble if it has one, or by matching a level line such as the bottom of a window.
- Line up the card's corner with the eave and see which printed line runs parallel to the rake edge.
How accurate it is
Expect to be within one pitch on a clear view. Accuracy drops on hip roofs, where you have no gable edge to sight, and on houses where trees or a second story block the line. Phone apps that overlay lines on the camera work the same way and share the same limits.
What people use it for
- Sanity checking a quote: if a proposal lists 10/12 and the card says 6/12, ask how it was measured.
- Planning safety: anything past about 7/12 is not a roof for a homeowner to walk.
- Reading an insurance estimate: estimates commonly add steep slope charges starting around 7/12, so the pitch on the estimate should match the house.
When a card is not enough
A card cannot see low slope porch roofs, dormers or the back side of the house. For a full roof, an attic measurement or an on-roof gauge reading for each plane is better. Read how roofers measure a roof and what to expect in a roof inspection.