Availability & Downtime Budget

The availability target applies to the scheduled hours entered.

This selection changes review context only. Formulas and example inputs stay unchanged. Check the model assumptions and applicability for the actual process.

Identify the actual asset, process, work boundary, source documents, units and assumptions. Confirm that the selected model or template applies before using its results.

1 Inputs

Minimum: 0 · Maximum: 100

Minimum: 1

Minimum: 0

2 Results

Allowed downtime / year
8.76 h
Per month
0.73 h
Per week
10.1 min
Per day
1.44 min
Achieved availability
100%
D = (1−A) × T; Aᵣ = (T−Dᵣ)/T
The availability target applies to the scheduled hours entered. Monthly and daily figures are averages, not separate allowances. Include zero actual downtime explicitly; compare the same scope of outages and operating time.

Worked example

Example values are illustrative. Replace them with your measured data.

InputValue
Target availability99.9 %
Scheduled operating time8760 h/year
Actual downtime (optional)0 h/year

Allowed downtime / year: 8.76 h

Related tools

About this calculator

How it works

You enter a target availability (%), scheduled operating hours per year and, optionally, actual downtime. Allowed downtime = (1 − target ÷ 100) × operating hours, split per month (÷12), per week (÷52) and per day (÷365). If you enter actual downtime, achieved availability = (hours − downtime) ÷ hours.

Worked example (illustrative inputs)

Target 99.9% on 8,760 h: allowed downtime = 0.001 × 8,760 = 8.76 h per year, about 10.1 minutes per week and 1.44 minutes per day.

How to read the result

Each extra nine cuts the budget by ten: on the same basis 99% allows 87.6 h and 99.99% about 53 minutes. With actual downtime entered, the tool shows whether you meet the target.

When to use it

Use it when agreeing an uptime target or service level, to turn a percentage into a downtime budget that maintenance planning can work with. Use the same hours basis that the target is defined against.

À propos de ce calculateur

Traduction (brouillon) — à relire.

Fonctionnement

Vous saisissez une disponibilité cible (%), les heures de fonctionnement prévues par an et, en option, l'arrêt réel. Arrêt autorisé = (1 − cible ÷ 100) × heures, réparti par mois (÷12), par semaine (÷52) et par jour (÷365). Si vous saisissez l'arrêt réel, disponibilité atteinte = (heures − arrêt) ÷ heures.

Exemple chiffré (valeurs d'illustration)

Cible 99,9 % sur 8 760 h : arrêt autorisé = 0,001 × 8 760 = 8,76 h par an, soit environ 10,1 minutes par semaine et 1,44 minute par jour.

Lire le résultat

Chaque « neuf » supplémentaire divise le budget par dix : sur la même base, 99 % autorise 87,6 h et 99,99 % environ 53 minutes. Avec l'arrêt réel, l'outil indique si la cible est atteinte.

Quand l'utiliser

Utilisez-le pour fixer une cible de disponibilité ou un niveau de service, afin de transformer un pourcentage en budget d'arrêt exploitable par la planification de maintenance. Utilisez la même base d'heures que celle de la cible.

حول هذه الحاسبة

ترجمة (مسودة) — للمراجعة.

طريقة الحساب

تُدخل الإتاحة المستهدفة (%) وساعات التشغيل المجدولة سنويًا، واختياريًا التوقف الفعلي. التوقف المسموح = (1 − الهدف ÷ 100) × الساعات، مقسّمًا شهريًا (÷12) وأسبوعيًا (÷52) ويوميًا (÷365). وإن أدخلت التوقف الفعلي فالإتاحة المحققة = (الساعات − التوقف) ÷ الساعات.

مثال محسوب (قيم توضيحية)

هدف 99.9% على 8760 ساعة: التوقف المسموح = 0.001 × 8760 = 8.76 ساعة سنويًا، أي نحو 10.1 دقيقة أسبوعيًا و1.44 دقيقة يوميًا.

قراءة النتيجة

كل «تسعة» إضافية تقسم الميزانية على عشرة: على الأساس نفسه تسمح 99% بـ 87.6 ساعة و99.99% بنحو 53 دقيقة. ومع إدخال التوقف الفعلي تبيّن الأداة هل تحقق الهدف.

متى تستخدمه

استخدمها عند الاتفاق على هدف إتاحة أو مستوى خدمة، لتحويل النسبة إلى ميزانية توقف يمكن لتخطيط الصيانة العمل بها. استخدم أساس الساعات نفسه الذي عُرِّف عليه الهدف.

In one line

The availability target applies to the scheduled hours entered. Monthly and daily figures are averages, not separate allowances. Include zero actual downtime explicitly; compare the same scope of outages and operating time.

Worked example

EXAMPLE

Illustrative values (the calculator defaults), not data from a real site.

Inputs
Target availability99.9 %
Scheduled operating time8760 h/year
Actual downtime (optional)0 h/year
Results
Allowed downtime / year8.76 h
Per month0.73 h
Per week10.1 min
Per day1.44 min
Service level3 nines

Frequently asked questions

How much downtime does 99.9% uptime actually allow?

On a 24/7, 8,760-hour basis, 99.9% allows about 8.76 hours of downtime per year, which works out to roughly 10 minutes per week. Moving to 99.99% cuts that down to under an hour a year.

Should I use 8,760 hours or my actual scheduled operating hours?

Use whatever basis your availability target is actually defined against. A true 24/7 continuous process should use 8,760 h/year, but if your plant runs on a defined schedule (say, two shifts, 6,000 h/year), enter that so the downtime budget reflects real operating time rather than calendar time.

What counts as downtime for this calculation?

That's up to your own definition and SLA — some organisations count only unplanned outages, others include planned maintenance windows too. Be consistent about what you include, since mixing planned and unplanned downtime will distort the achieved-availability comparison.

Is a higher availability target always better?

Not necessarily — each additional nine costs roughly ten times more in redundancy, spares and maintenance rigor to sustain, while the downtime budget shrinks by the same factor. Setting an unrealistic target you can't consistently hit just creates chronic SLA breaches; it's usually better to set an achievable target and improve it over time.

How do I know if I'm actually meeting my target?

Enter your measured actual downtime for the same period and the tool computes your achieved availability and compares it directly against the target, flagging a pass or fail — this is the same math used in reverse, so it's an apples-to-apples comparison.

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