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How many lifts does your building actually need?

An up-peak calculation to AS ISO 8100.32:2026, benchmarked against the Property Council grading your building will be judged on. Every figure is shown and every assumption is named — so you can take the numbers to your architect, not just take our word for it.

Benchmark

Judge against

Building

Floors served above entrance

Floor height m

Population served persons

Office type CIBSE / ISO Table 4

Net internal area m², total above entrance

Lift group

Number of lifts

Rated capacity persons

Rated speed m/s

Loading limit F_l

Timing

Door width sets t_p, ISO Table 6

Performance time t_perf

This building is outside the calculation method

AS ISO 8100.32 clause 5.3 says a design is complex — and requires simulation rather than calculation — when any of the following apply:

—

—

—Up-peak interval

—Handling capacity

—CIBSE quality of serviceby interval

—Lifts needed to pass

Working	Value
P — passengers per trip (F_l × capacity)	—
S — probable stops	—
H — highest reversal floor	—
t_v — single-floor transit time	—
t_s — time consumed per stop	—
t_rt — round trip time	—
t_nt — nominal travel time (speed check)	—
Q — smallest car that suits P (ISO Table A.1)	—

The method, and where it stops

Up-peak round trip time, AS ISO 8100.32:2026 (ISO 8100-32:2020) Formula (12):

t rt = 2 · H · t v + (S + 1) · t s + 2 · P · t p

Probable stops, Formula (17), and highest reversal floor, Formula (18), for even population distribution:

S = N · [1 − ((N−1)/N)^P] H = N − Σ(i=1..N−1) (i/N)^P

Interval, Formula (10), and handling capacity, Formulae (9) and (11):

t int = t rt / L C h = 300 · P · L / t rt %C h = C h / U

t v = d f / v n, t s = t perf − t v and P = F l × rated capacity. Checked against the standard's own Annex D worked example: at N = 13 and P = 13.1 this returns S = 8.44 and H = 12.50 against the printed 8.4 and 12.5, and reproduces the printed round trip time of 164.9 s exactly.

Clause 6.3.1 is explicit that no allowance is made for absenteeism or stair use — the criteria are based on 100% of the building population, so that is what this calculates on.

What this is, and what it isn't. This is the calculation method: pure up-peak, one entrance at the lowest floor, even population bias per floor, identical lifts, conventional group control. It is genuinely useful for sanity-checking a scheme early. It is not a traffic study. The Property Council criteria your building will actually be graded against are written in average waiting time, and waiting time cannot be derived from a round trip time — it has to be simulated over a full traffic template. That is the difference between this page and the report we'd issue.

Sources. Method and criteria: AS ISO 8100.32:2026, identical adoption of ISO 8100-32:2020 — Tables 2, 4, 6, 7 and A.1, Formulae (9)–(18). Office grading: Property Council of Australia, A Guide to Office Building Quality, 2019, 3rd edition. Quality-of-service bands: CIBSE Guide D.
PCA targets are waiting times, not intervals. Premium 25 s and Grade A 30 s are average waiting times at up-peak on 100% population. This page reports interval, which is a different quantity. Where you've selected a PCA benchmark, the interval is compared against the AS ISO 8100.32 office target of ≤30 s and the PCA handling capacity is applied as-is — the waiting-time test is flagged as outstanding, because it honestly is.
Car sizing. ISO selects the car on mass and area — 75 kg and 0.21 m² per person, with F_l at or below 0.8. Table 2's targets assume both checks were done; if the car was picked on mass alone, the standard says to aim higher than the tabled handling capacity.

The rest of what we do

Most people don't arrive here designing a building. They arrive here with a lift problem.

The calculator answers one narrow question. These are the ones we get asked far more often — and the assistant in the corner will take you through any of them.

Audit

Are you getting the maintenance you're paying for?

We attend site, inspect the equipment against the contract and AS 1735, and pull the callback history. It's the fastest way to find out whether a lift that keeps stopping is worn out or simply under-maintained — and the two look identical from the lobby.

Mediation

Stuck with a contractor who won't move?

We act as the independent technical party between you and the lift company — response times, variation invoices under a comprehensive contract, disputed scope, an upgrade you're being pushed towards. Most of it settles once someone is reading the contract and the service records properly.

Tender

One specification, priced by everyone.

A modernisation quoted by the incumbent with nothing to price it against is the most common way owners overspend. We write the scope, run it competitively, and the fee is usually a fraction of the spread between the first price and the best one.

Study

The figure that actually gets signed off.

Up-peak, mixed and lunch traffic simulated over a full template, against the Property Council criteria your building is graded on, plus NCC car sizes, stretcher provision and DDA. Lunch peak is where schemes fail, and no calculation will find it.