Methodology

We don’t hide assumptions inside the answer.

Every number on this site carries a label saying where it came from. Here is what each label means, and what a reference check is not.

A construction calculator is only worth trusting if you can see what went into the answer. So each figure on a result carries one of five labels, and the sources and assumptions sit on the page rather than behind a link.

How these numbers are made

  1. Stage 1

    Mathematics & geometry

    The result the engine computed from your inputs, using the formula shown on the page.

  2. Stage 2

    Construction rules & conventions

    A limit taken from a published standard, with its edition and section named.

  3. Stage 3

    Manufacturer data

    A figure from a product data sheet — a bag yield, a shingle coverage — attributed to the product it came from.

  4. Stage 4

    Reference profiles

    A reference check is not a compliance determination; local amendments differ.

  5. Stage 5

    Visible assumptions

    These are the figures we are least certain of, and they say so rather than hiding among the others.

What each label means

CALCULATED
The result the engine computed from your inputs, using the formula shown on the page. No rounding beyond what is displayed, and the exact value is what every other figure is derived from.
Volume 2.37 yd³ from 16' 0" × 12' 0" × 4"CALCULATED
CODE REFERENCE
A limit taken from a published standard, with its edition and section named. We check against the standard you select; we do not determine which code governs your project.
Maximum riser height 7 3/4" — R311.7.5.1, 2021 IRCCODE REFERENCE
MFR SPEC
A figure from a product data sheet — a bag yield, a shingle coverage — attributed to the product it came from, because a generic figure and a product figure are not the same number.
Bag yield 0.60 ft³ per 80-lb bagMFR SPEC
SUGGESTED DEFAULT
A value we filled in so the calculator runs, which you are expected to change: a waste allowance, a stock length. It is labelled so it never passes for a measurement you gave us.
Waste allowance 10%SUGGESTED DEFAULT
ASSUMPTION
A convention we applied because no source states it. These are the figures we are least certain of, and they say so rather than hiding among the others.
Nosing is excluded from the total runASSUMPTION

The Result Block

Stair Stringer · Result

Calculated

RISERS × TYPICAL RISER

7 risers at 6 and seven eighths inches

Total run
5' 0"
Throat
5 5/8"
Cut length
6' 0 3/4"
Stock
8'

2021 IRC reference check — within the limits checked. Local requirements may differ.

Reference profile 2021 IRCA reference check is not a compliance determination; local amendments differ.

Setting

Standard stock lengths 8/10/12/14/16/20 ft are a market convention

SUGGESTED DEFAULT
Code references & assumptions · 3

How this result is supported

Everything behind this result. Nothing here is hidden inside the number.
SUGGESTED DEFAULTStandard stock lengths 8/10/12/14/16/20 ft are a market convention
UNVERIFIED
CODE REFERENCEMaximum riser height 7 3/4 in — R311.7.5.1, 2021 IRC
PRIMARY-VERIFIED
ASSUMPTIONNosing is excluded from the total run; finished flooring thickness is not modelled
UNVERIFIED
What do these evidence labels mean?
PRIMARY-VERIFIED
directly supported by one authoritative primary source, quoted with section/page/figure
CROSS-VERIFIED
independently supported by two or more appropriate authoritative sources
DERIVED
mathematically derived from PRIMARY-VERIFIED values; the derivation is preserved in data and in code
INTERPRETED
a source exists but translating it into calculator behaviour required interpretation
CONVENTION
recognised trade practice, not a mandatory provision
ASSUMPTION
product/design assumption or useful default with no authoritative basis
UNVERIFIED
insufficient authoritative evidence
Full methodology →

Code references and product data are quoted in the units their source uses.

Reference checks are informational, not compliance determinations.

  1. Tier 1

    Result

    The answer, its label and the status chip.

  2. Tier 2

    Reference check

    What was checked, against which standard.

  3. Tier 3

    Assumptions/defaults

    The values that shaped the answer and that you can change.

  4. Tier 4

    Sources disclosure

    Everything behind the result, in full.

Reference profiles

ProfileEditionScopeProvisions checked
2021 IRC2021 International Residential Code2021One- and two-family dwellings and townhouses; conventional light-frame wood constructionR311.7.1, R311.7.2, R311.7.3, R311.7.5.1, R311.7.5.2 (screenshots 01–03) · R502.8.1 (screenshot 54), reached for rafters via R802.7.1 (screenshot 50) · R802.4.4 and R802.6 (screenshot 50)
Wisconsin SPS 321Wisconsin Administrative Code ch. SPS 321 (Uniform Dwelling Code)Register May 2022 No. 797One- and two-family dwellings in WisconsinSPS 321.04 (p7) · SPS 321.27 notching subd. 2–3 · SPS 321.27 (1) (b)
  • 2021 IRC: A reference check against the 2021 IRC, not a determination of the code governing this project: adoption, local amendments, occupancy and building type are not modelled.
  • Wisconsin SPS 321: A reference check against Wisconsin SPS 321 as published in May 2022, not a determination of the code governing this project: municipal amendments, adoption dates and occupancies outside the Uniform Dwelling Code are not modelled.

What a reference check is not

A reference check compares your inputs against the provisions of one published standard, in one edition, for the scope that standard covers. It does not know which code your jurisdiction has adopted, what local amendments apply, or whether your project is within that code’s scope at all. It is a way of noticing that a number is close to a limit, not a substitute for the person who signs off the work.