RCD Trip Calculator — estimate rcd trip for your project. Fast, accurate, free. No signup required.
An RCD trip check compares residual-current protection with a measured test result. The rated residual operating current, actual trip current, and trip time answer different questions and should be recorded separately on an electrical test schedule. The RCD Trip calculator keeps the topic-specific quantities visible so you can audit the assumptions before using the result.
Construction estimates are highly sensitive to site conditions, product specifications, local policy, and the stage of design. A useful early estimate states its units, boundary, design allowance, and source of any reference value. It should help you ask a better question of a supplier, designer, building-control officer, planning authority, or installer—not pretend that a three-field calculation is a signed design.
Use the related construction calculator for an adjacent check and the companion standards calculator when the result crosses into quantities, structure, services, energy, water, or regulation. Keep the original dimensions and assumptions with the displayed output so a later revision can be compared on like-for-like terms.
Where the page gives a consent, fire, electrical, accessibility, heritage, or safety prompt instead of a single number, that is deliberate. Those topics depend on documents, inspections, local rules, tested products, and professional judgement. The calculator can organise the first pass, but it cannot issue an approval or replace a competent person's review.
Indicative pass check: measured trip current must be below the rated residual current and measured trip time must be within the applicable test limit.
The formula is intentionally shown beside the inputs. Convert millimetres, metres, kilowatts, amps, percentages, and category scores consistently, and keep intermediate precision until the final display. A plausible-looking answer can still be unusable if a clear opening was confused with an outside frame, a nominal capacity with a tested rating, or a planning assumption with a statutory threshold.
For site work, the formula is the beginning of the check rather than the complete specification. Add the conditions that control the real decision: subgrade and drainage for roads, grouping and installation method for cables, weather and emitter temperature for heat pumps, significance for heritage, occupancy for escape, and local policy for planning matters.
Inputs used here: RCD rated residual current, measured trip current, and measured trip time. Keep each input traceable to a drawing, survey, test result, product sheet, policy document, or clearly marked planning assumption.
The result is an indicative interpretation of the entered test values. It is not a substitute for a calibrated instrument, the correct test sequence, polarity checks, earth-fault-loop assessment, or the requirements of the particular RCD type.
Check direction and order of magnitude before relying on the result. A larger opening should increase area, a longer cable should increase voltage drop, a higher COP should reduce electrical input, a wider exit should increase the indicative capacity, and a higher traffic class should demand a stronger cover or pavement solution. If a change behaves the other way, recheck the units and the field mapping.
Do not report more precision than the survey or input supports. Round a procurement quantity up where the supplier sells discrete sizes, preserve the unrounded design calculation for review, and label any result based on a default rate or simplified weighting. If the number affects structural stability, fire safety, electric shock protection, accessibility, legal consent, or a regulated rating, stop at the estimate and obtain the appropriate review.
RCD testing and fault diagnosis should be carried out by a competent electrician with calibrated equipment and appropriate isolation procedures. This calculator provides preliminary educational guidance only and does not constitute a structural design, electrical certificate, fire strategy, planning decision, Building Regulations approval, heritage consent, accessibility audit, or certified sustainability assessment.