Standards, formulas, unit conversions, and terminology behind all 19 CalcType calculators — a quick reference for landscape architects working across UK, EU, and North American practice.
01 — Reference
Standards Library
Every code, standard, and technical guideline cited across the 19 calculators, grouped by discipline. Each calculator page lists the exact clauses it applies.
Acoustics & Vibration
Used in: Acoustic & Noise Barrier
ISO 9613-2 — outdoor sound propagationInternational
BS 4142:2014+A1 — rating industrial/commercial noiseUK
BS 8233:2014 — sound insulation for buildingsUK
BS 6472-1:2008 — human exposure to vibrationUK
CRTN (DoT 1988) — calculation of road traffic noiseUK
DIN 4150-3 — vibration effects on structuresEU
Playground & Recreation Safety
Used in: Playground Safety, Pool & Water Feature
EN 1176 / EN 1177 — playground equipment & impact-absorbing surfacingEU
ASTM F1487-21 — playground equipment for public useUS
AS 4685:2017 — playground equipmentInternational
RoSPA Inspection Guidelines — playground inspection practiceUK
PWTAG 2021 — pool water treatmentUK
WHO Recreational Water Vol. 2 — pool & water qualityInternational
Structural & Geotechnical
Used in: Structural Safety, Soil Load & Traffic, Site Grading
Eurocode 7 (EN 1997-1) — geotechnical designEU
Eurocode 5 (EN 1995-1) — timber structuresEU
Eurocode 1 (EN 1991-1-4) — wind actionsEU
ASTM D698 — standard Proctor compactionUS
AASHTO T99 / AASHTO 93 — soil & pavement designUS
BS 1377 — soil testing methodsUK
BS 5837:2012 — trees in relation to design/constructionUK
IBC 2021 — occupancy & structural provisionsUS
Accessibility & Circulation
Used in: Circulation & Capacity, Structural Safety
ADA Standards 2010 — accessible designUS
BS 8300:2018 — inclusive/accessible built environmentUK
EN 17210:2021 — accessibility of the built environmentEU
LTN 1/20 (DfT) — cycle infrastructure designUK
HCM 7th Edition — highway capacity manualUS
NFPA 101 / BS 9999 — life safety & fire egressInternational
Water, Drainage & Irrigation
Used in: Stormwater & Hydrology, Irrigation & Water Management
CIRIA C753 — SuDS ManualUK
FAO-56 Penman-Monteith — reference evapotranspirationInternational
ASABE S436.1 — irrigation system designUS
TR-55 (NRCS) — urban hydrology for small watershedsUS
BS EN 752 — drain and sewer systemsEU
AWWA Manual M22 — sizing water service linesUS
Sustainability & Carbon
Used in: Carbon Sequestration, Embodied Carbon
RICS WLCA 2023 — whole life carbon assessmentUK
BS EN 15978 — sustainability of construction worksEU
ICE Database v3.0 — embodied carbon (Bath/BEIS)UK
IPCC Tier 1 — greenhouse gas accountingInternational
LEED v4.1 / BREEAM 2018 — green building ratingInternational
PAS 2080 — carbon management in infrastructureUK
Lighting & Electrical
Used in: Lighting & Electrical Load
IESNA RP-33 — roadway lighting practiceUS
EN 13201 — road lightingEU
BS 5489 — lighting of roads and public amenity areasUK
NEC / NFPA 70 — national electrical codeUS
IEC 60364-7 — low-voltage electrical installationsInternational
ASHRAE 90.1 — energy standard for buildingsUS
Materials & Pavements
Used in: Hardscape & Material, Soil Load & Traffic
BS 7533 — pavement design for clay/concrete paversUK
BS 8500 — concrete specificationUK
ASTM C936 — interlocking concrete paversUS
HA 104 — design of pavement foundationsUK
BS EN 1340 / BS EN 771 — concrete kerbs & masonry unitsEU
Vegetation, Soil & Green Roofs
Used in: Planting & Vegetation, Soil & Amendment, Green Roof
BS 8545:2014 — trees: nursery to independenceUK
BS 3882:2015 — topsoil specificationUK
GRO Green Roof Code 2021UK
FLL Guideline 2018 — green roof design (Germany)EU
ASTM E2396 — green roof water capture testingUS
i-Tree Eco — urban forest ecosystem analysisInternational
Solar, Daylight & Wind
Used in: Shadow & Solar Analysis, Wind Comfort
NOAA Solar Position AlgorithmInternational
BRE 209 — site layout planning for daylight/sunlightUK
CIBSE AM11 — building performance modellingUK
Lawson Wind Comfort Criteria (2001)International
ASCE 7-22 — minimum design loadsUS
ISO 7730 — ergonomics of the thermal environmentInternational
Cost & Project Management
Used in: Cost Estimating & Budgeting
RICS NRM1 / NRM2 — order of cost estimating & cost planningUK
RIBA Plan of Work 2020UK
ISO 15686 — life cycle costingInternational
CIOB Code of Estimating PracticeUK
02 — Reference
Formula Reference Sheet
The core engineering relationships behind CalcType’s results — for verification, teaching, or when you just need the equation without opening the tool.
Rational Method — Peak Flow
Stormwater
Q = C × I × A / 360 (L/s, I in mm/hr, A in m²)
C = runoff coefficient, I = rainfall intensity for the design storm, A = catchment area. Foundation of the Rational Method calculator’s peak-flow tab.
Manning’s Equation — Open Channel Flow
Stormwater
V = (1/n) × R^(2/3) × S^(1/2) Q = V × A
n = channel roughness, R = hydraulic radius (area / wetted perimeter), S = longitudinal slope. Used for swale and channel capacity checks.
Hazen-Williams — Pipe Friction Loss
Irrigation & Pool
hf = 10.67 × L × Q^1.852 / (C^1.852 × d^4.87)
C = pipe material roughness coefficient, d = internal diameter (m). Drives pressure-loss and pump-duty calculations.
FAO-56 Crop Water Need
Irrigation
ETc = ETo × Kc
Reference evapotranspiration (ETo) scaled by a crop/planting coefficient (Kc) to give actual irrigation demand.
Sabine’s Reverberation Time
Acoustic
RT60 = 0.161 × V / ΣAα
V = room volume (m³), ΣAα = total absorption (sum of each surface area × its absorption coefficient).
Maekawa Barrier Insertion Loss
Acoustic
IL = 10 × log₁₀(3 + 20N) N = 2δ/λ
δ = path-length difference created by the barrier, λ = sound wavelength. N is the Fresnel diffraction number.
ISO 9613-2 Distance Attenuation
Acoustic
Lp = Lw − Adiv − Agr − Aatm
Sound power level reduced by geometric divergence, ground effect, and atmospheric absorption to give the level at the receiver.
Rankine Active & Passive Earth Pressure
Structural
Ka = (1−sinφ)/(1+sinφ) Kp = (1+sinφ)/(1−sinφ)
φ = angle of internal friction of the retained soil. Ka drives overturning/sliding checks on retaining walls; Kp gives passive toe resistance.
Infinite Slope Factor of Safety
Structural / Site Grading
FoS = (c + (γH cos²β − ruγH) tanφ) / (γH sinβ cosβ)
c = cohesion, γ = unit weight, H = slope height, β = slope angle, ru = pore pressure ratio. FoS ≥ 1.5 is a typical target for permanent slopes.
Boussinesq Vertical Stress
Soil Load & Traffic
σz = q × (1 − (z / √(r²+z²))³)
Stress at depth z beneath a circular surface load of intensity q and radius r — used to check root-zone compaction risk under vehicle loading.
Cut & Fill — Average End Area
Site Grading
V = (A1 + A2) / 2 × L
A1, A2 = cross-sectional areas at each station, L = distance between stations. The prismoidal method (V = L/6 × (A1+4Am+A2)) is more accurate for variable sections.
Illuminance from Luminaire Flux
Lighting
Eavg = (Φ × qty × CU × LLF) / Area
Φ = luminous flux (lm) per fitting, CU = coefficient of utilisation, LLF = light loss factor accounting for lamp depreciation and dirt.
Voltage Drop
Lighting
Vdrop = I × Rcable Rcable = ρ × 2L / A
ρ = cable resistivity (copper/aluminium), L = one-way run length, A = conductor cross-section. Compared against the 3–5% statutory limit.
PPV Ground Vibration Attenuation
Acoustic / Vibration
PPV2 = PPV1 × (10/d)^n
n = ground attenuation exponent (typically 1.0–1.7 depending on soil type). Estimates peak particle velocity at distance d from a 10m reference measurement.
Trapezoidal Swale Cross-Section
Stormwater / Site Grading
Area = (b + zH) × H Top width = b + 2zH
b = bottom width, H = depth, z = side-slope ratio (H:1V). Feeds directly into the Manning’s equation capacity check above.
03 — Reference
Unit Conversions
Every calculator includes a live Metric/Imperial “Unit Type” switch. Internally, all standards checks always run in metric — this table is the same conversion basis used throughout the site.
| Quantity | Metric | Imperial | Conversion |
|---|---|---|---|
| Length | 1 m | ft | 1 m = 3.281 ft |
| Small dimension / depth | 1 mm | in | 1 mm = 0.0394 in |
| Area | 1 m² | ft² | 1 m² = 10.764 ft² |
| Volume | 1 m³ | ft³ | 1 m³ = 35.315 ft³ |
| Liquid volume | 1 litre | US gal | 1 L = 0.2642 US gal |
| Flow rate | 1 L/min | US gpm | 1 L/min = 0.2642 gpm |
| Mass | 1 kg | lb | 1 kg = 2.205 lb |
| Mass (bulk) | 1 tonne | US ton | 1 t = 1.102 US ton |
| Temperature | °C | °F | °F = °C × 9/5 + 32 |
| Pressure | 1 bar | psi | 1 bar = 14.504 psi |
| Pressure | 1 kPa | psi | 1 kPa = 0.145 psi |
| Velocity | 1 m/s | mph | 1 m/s = 2.237 mph |
| Speed | 1 km/h | mph | 1 km/h = 0.621 mph |
04 — Reference
Glossary
Plain-language definitions for the technical terms used across CalcType.
Critical Fall Height (CFH)
The vertical distance from the highest accessible point of play equipment to the impact-absorbing surface below — the figure that sets the required surfacing depth and use-zone size.
Rw (Weighted Sound Reduction Index)
A single-number rating of how well a building element — a wall, window, or door — blocks airborne sound. Higher Rw means better insulation.
PPV (Peak Particle Velocity)
The maximum speed at which a point in the ground moves during a vibration event, typically in mm/s — the standard metric for assessing construction or traffic vibration.
VDV (Vibration Dose Value)
A cumulative measure of vibration exposure over a period of time, used to assess human comfort rather than structural risk.
Manning’s n
A roughness coefficient describing how much a channel or pipe surface resists water flow — higher n means rougher, slower flow.
Runoff Coefficient (C)
The fraction of rainfall on a surface that becomes runoff rather than infiltrating — close to 1.0 for paving, much lower for vegetated ground.
Time of Concentration (Tc)
The time it takes water to travel from the most hydraulically distant point of a catchment to the point of interest — used to select the design rainfall intensity.
Coefficient of Utilisation (CU)
The proportion of light emitted by a fitting that actually reaches the working plane, after losses to the room or site geometry.
Light Loss Factor (LLF)
An allowance for the gradual reduction in light output over a fitting’s life, due to lamp depreciation and dirt accumulation.
Embodied Carbon (A1–A5, B, C, D)
The greenhouse gas emissions associated with a material or building across its life cycle stages: production (A1–A3), transport & construction (A4–A5), use (B), end of life (C), and benefits beyond the system boundary (D).
Sequestration Rate
The rate at which vegetation removes and stores atmospheric carbon dioxide, usually expressed in kg CO₂/year per plant or per unit area.
Factor of Safety (FoS)
The ratio of a structure’s resisting capacity to the forces acting on it. A FoS of 1.5 means the structure can resist 50% more load than the design case before failing.
Active / Passive Earth Pressure
Active pressure is the force soil exerts on a retaining wall as it pushes outward; passive pressure is the resistance the soil in front of the wall’s toe provides against movement.
Use Zone
The surfaced area around playground equipment that must remain clear and impact-absorbing, sized according to the equipment’s critical fall height.
Attenuation
The reduction in a signal’s strength — of sound, vibration, or stormwater flow — as it travels through a medium or a control measure.
Distribution Uniformity (DU)
A measure of how evenly an irrigation system applies water across a zone. Higher DU means less over- or under-watering across the coverage area.
Reverberation Time (RT60)
The time it takes for sound in a room to decay by 60 decibels after the source stops — the standard measure of a space’s acoustic liveliness.
Rating Level (LAr,Tr)
Under BS 4142, the specific sound level of a noise source adjusted for tonal or impulsive character penalties, compared against background level to judge likely impact.
Fresnel Number (N)
A dimensionless value describing how effectively a barrier diffracts sound around it — larger N means greater insertion loss from the barrier.
Hydraulic Radius (R)
The cross-sectional area of flow divided by the wetted perimeter of a channel — a key input to Manning’s equation for flow velocity.
05 — Reference
How to Use CalcType
Quick answers to how the calculators actually work.
What does the “Unit Type” dropdown do?
It switches every input and result on that calculator between Imperial (ft/in) and Metric (m/cm) display. Internally, every calculation always runs in metric — since the underlying standards (EN, ISO, BS) are metric-based — so switching units never changes your results, only how they’re displayed. The setting applies across all tabs of a calculator at once.
Do I need to press a button to calculate?
No. Every field recalculates live as you type or make a selection — there is no submit button anywhere on the site.
What is the “Print / Save as PDF” button for?
It opens your browser’s print dialog with a clean, white-background version of the current tab’s results — formatted for a physical printout or a “Save as PDF” export, ready to attach to a report or send to a client.
Can I add or remove rows in tools like Cost Estimating or Irrigation?
Yes — any list-style input (equipment schedules, plant groups, catchment surfaces) has an “Add” control to insert another row and a “Remove” control on each row. Totals and results update immediately.
Which standard should I follow if two give different answers?
Where a calculator checks a value against more than one code (for example EN 1176 and ASTM F1487 on the same playground equipment), it shows every relevant standard’s threshold separately rather than picking one — apply whichever governs your project’s jurisdiction or client requirement.
Are the calculators mobile-friendly?
Yes — every tool, including this reference page, is built to work on a phone or tablet: tabs wrap instead of requiring horizontal scrolling, and result cards stay readable at narrow widths.
06 — Reference
Professional Use
CalcType’s calculators are design aids, built to speed up early-stage sizing, feasibility checks, and coordination between disciplines. They are not a substitute for the judgement, site-specific investigation, or sign-off of a qualified, chartered, or licensed professional.
Structural, geotechnical, drainage, and life-safety calculations in particular should always be verified and stamped by the relevant registered engineer before construction. Standards referenced throughout this site are summarised for design guidance — always consult the current, full published standard for any figure that will appear in a submitted or built design.
Formulas and coefficients used across CalcType draw on publicly documented engineering methods and the standards listed in the library above. If you find a figure that looks wrong, we want to know — every calculator includes a way to flag feedback.