How We Calculate

Sources and verification

Each reference value comes from a source recorded with its date of checking: legislation, public technical manuals, tables published by public agencies and manufacturers' data sheets. Sources were last checked on 25 Oct 2026. A value that is not checked again in time stops the site from being rebuilt until it is.

Where a source is secondary, for example commentary on a contract form, the text names it. The German pages cite VOB/B from a published copy until the printed text has been checked, and say so there. Contract forms and standards (JCT, NEC, FIDIC, AIA, RICS, AS 4000, ASTM, BS, EN) are named and described in our own words, never copied.

Freshness rule

next check ≤ last check + 183 days

A value past this date fails the build until it has been checked again.

Daily report

Man-hours come from the crew lines and lost hours from the delay lines. Equipment hours are kept apart from labor.

Gross man-hours

H = Σ (workers × hours)

Summed over all crews of the day.

Lost man-hours

L = Σ (affected workers × delay hours)

A delay may not affect more workers than were on site or last longer than the longest shift; together the delays may not exceed H.

Utilization

U = (H − L) / H × 100

Shown as n/a when no workers are entered.

Punch list

Counts use the status and due date of each item on the inspection date.

Closed share

C = (fixed + accepted) / total × 100

Shown as n/a for an empty list.

Overdue

open and due date < inspection date

An item due on the inspection date is not overdue.

Open cost

K = Σ estimated cost of open items

Items without an estimate count as 0, with a warning.

Daywork sheet

Labor, plant and materials are priced separately; each group has its own percentage addition, and tax is applied to the total.

Line

a = number × hours × rate, or quantity × unit price

Rounded to cents.

Group

G = Σ a + round(Σ a × addition % / 100)

Additions are contract values you enter.

Total

T = Σ G + round(Σ G × tax % / 100)

No default tax rate on the English pages.

Training matrix

Each required certificate gets one status on the report date. Dates are compared as whole calendar days, without times.

Days to expiry

D = expiry date − report date

Valid up to and including the expiry date, expired from the next day.

Status

expired if D < 0; expiring if 0 ≤ D ≤ warning days; valid otherwise

No expiry date = valid; required but not entered = missing.

Compliance

C = (valid + expiring) / required × 100

Certificates not required for a role are not counted.

Retention and payment

All values are cumulative to date. Rate, cap and release share are contract values you enter.

Gross value

V = work done + approved variations + materials on site

Variations may be negative, V may not.

Retention

R = min(V × rate, contract sum × cap)

Without a cap, R = V × rate.

Amount due

P = V − R − advance recovered to date − previously certified

A negative P is shown with a warning.

Release

R1 = R × release share; R2 = R − R1

R1 at completion, R2 after the defects period.

Concrete and excavation

Geometry first, then waste, then whole loads, bags and trips. Units are converted with exact factors: 1 ft = 0.3048 m, 1 in = 0.0254 m, 1 yd³ = 27 ft³.

Element volume

slab, footing, wall: L × W × t; round column: π / 4 × d² × h

Times the number of elements.

Volume to order

V order = V × (1 + waste % / 100)

1 yd³ = 0.764555 m³.

Loads, bags, trips

n = V / capacity, rounded up

A floating-point excess below 0.000000001 is ignored, so an exact multiple is not rounded up.

Loose soil

V loose = V bank × bulking factor

Suggested factors from US Army FM 5-434 (2000), Table 1-1; you can change them.

Rebar weight

Metric bars by formula from the nominal diameter, US bar sizes from the ASTM A615 table as published by Caltrans.

Metric bars

m = π / 4 × d² × 7,850 kg/m³ ≈ d² / 162.2 (kg/m, d in mm)

The two forms agree within 0.01 %; the calculator uses the full formula.

US bar sizes

w = table weight (lb/ft); kg/m = lb/ft × 1.488164

Table values, not a formula.

Total

M = Σ (count × length × mass per length) × (1 + allowance % / 100)

Grouped by size.

Rounding

Money is rounded to cents in each printed line, and totals are built from the rounded lines, so a printed sheet always adds up. Hours, volumes and weights are kept unrounded and rounded only for display: usually two decimals, three for kg/m. Counts of loads, bags and trips are rounded up.

Commercial rounding

round(x) = x to 2 decimals, halves away from zero

For example, 176.025 becomes 176.03.

Limitations

The calculators assume that the inputs are right: dimensions as built, hours as worked, rates as agreed. They do not check structural adequacy, contract entitlement or legal compliance. Values that are only examples, such as daywork additions or the share of retention released at completion, are marked as contract parameters and should be replaced with your own.