Daftary offers calculators on topics that touch people’s money, health and worship, so you have a right to know how each result is calculated, where its rules come from, and how we check it. This page brings all of that together.
Last reviewed: September 2026Our principles
- Every rule has a stated source: we rely on official legal texts, published scientific formulas and recognised works of fiqh, and we name the source in each calculator’s explanation.
- We present views; we don’t issue fatwas: on religious questions we follow the majority of scholars, show other recognised views where the difference matters, and leave rulings on special cases to scholars.
- We state each calculator’s limits: under every tool, a note says who it is for, when it doesn’t apply, and which authority has the final word.
- Your data stays on your device: every calculation runs in your browser, and the numbers you type are never sent to a server.
How we check the calculations
- Before publishing: we work through each tool by hand on known examples from the sources and match the calculator’s result figure by figure.
- Automated tests: more than 300 automated checks run on every site update, covering calculation accuracy, links, mobile layout and offline use.
- Independent review: the most demanding calculators, such as inheritance, get a separate review by someone who didn’t build them.
Regular reviews
- Every three months: we review VAT rates, end-of-service laws and gold taxes, and update anything that has changed.
- Every Hijri year: we update Ramadan and Eid dates when they are officially announced.
- Whenever you report something: we check every reported error and fix it.
Sources by calculator
Islamic calculators
| Calculator | Source |
|---|---|
| Zakat | Nisab of 85 g of pure (24k) gold, the majority view, with an option for 85 g of 21k used by Egypt’s Dar al-Ifta; rate 2.5%. |
| Inheritance | Sunni fara’id: fixed shares, residuaries, exclusion, ‘awl and radd, plus special cases such as al-‘Umariyyatain, al-Mushtaraka and al-Akdariyya. For disputed cases (such as the grandfather with siblings) you can choose a madhhab. Checked against 60 textbook cases, then an independent review of about 80 cases. |
| Zakat al-Fitr | One sa‘ as described by the jurists, with the difference of opinion on paying its value in cash, and a reminder to match your country’s official fatwa body. |
| Missed fasts and fidyah | The majority view that missed fasts are made up before the next Ramadan, the difference of opinion on feeding when delayed, and fidyah for permanent excuses. |
| Kaffarah | The order of expiation for broken oaths, deliberately breaking a Ramadan fast, and dhihar, as held by the majority of jurists. |
| Tasbeeh counter | Dhikr hadiths from Sahih al-Bukhari and Sahih Muslim with their numbers (Muslim 597, 2691, 2702, 408; Bukhari 6403, 6405, 6406). |
| Last third of the night | Sun-position formulas (PrayTimes) with each country’s official fajr angle: Egyptian General Authority of Survey 19.5°, Umm al-Qura 18.5°, UAE Awqaf 18.2° (maghrib +3 min), and 18° for Kuwait and Qatar. Matches published timetables for Cairo, Makkah and Abu Dhabi. |
| Prayer times | Solar position formulas (PrayTimes.org) with the Egyptian General Authority of Survey method for Egypt (Fajr 19.5°, Isha 17.5°) and Umm al-Qura for Saudi Arabia (Fajr 18.5°, Isha 90 minutes after Maghrib, 120 in Ramadan). Checked against Dar al-Ifta’s table for every day of September 2026 and the Survey Authority’s table for 15 governorates: never more than 1 minute off. |
| Qibla direction | Great-circle initial bearing from the location to the Kaaba (21.4225 N, 39.8262 E), from true north; distance with an Earth radius of 6,371 km. |
| Quran khatma planner | Madinah mushaf data (604 pages): where each juz and surah begins and the first ayah on every page, from the open-source Quran.com Android app, with all 114 surah names checked. Ramadan dates from the Umm al-Qura calendar. |
Money and work
| Calculator | Source |
|---|---|
| End of service — Saudi Arabia | Saudi Labor Law: Article 84 (half a month per year for the first five years, then a full month), Article 85 (resignation fractions), Article 87 (full-award cases) and Article 80. |
| Gratuity — UAE | Article 51 of Federal Decree-Law No. 33 of 2021: 21 days’ wage per year for the first five years, 30 days after, capped at two years’ wage. |
| VAT | Standard rates published by each country’s tax authority, reviewed every three months. |
| COD order profit | Cash-on-delivery order economics: delivered orders = orders × confirmation rate × delivery rate; net after product cost, shipping, returns, fees and ads. The calculator uses the user’s own figures and assumes no “typical” rates. |
| Loans | The standard amortisation formula on a reducing balance, and the flat-rate method used in many bank offers. |
| Cash vs installments | An internal-rate-of-return calculation that shows the real annual rate of an installment plan. |
| Car finance | The common bank method for flat (murabaha) rates: profit = financed × rate × years, balloon at the end, and the true rate solved from the cash flows on a reducing balance (insurance excluded), as in the installment calculator. |
| Stock average | Plain arithmetic, weighted-average cost: average = (Σ price × shares + buy commission) ÷ Σ shares. Break-even = cost ÷ (shares × (1 − commission)). Averaging down: shares = (cost − target × shares) ÷ (target − buy price incl. commission), rounded up. The commission is the user’s own broker percentage; no broker rates are printed. Bonus shares are a row at price 0. |
| Gratuity — Qatar | Article 54 of Qatar Labour Law No. 14 of 2004: at least three weeks’ basic wage per year after one year of service, and Article 61 for forfeiture. |
| Indemnity — Kuwait | Articles 51 and 53 of Private Sector Labour Law No. 6 of 2010: 15 days’ wage per year for the first five years and a month after, capped at 18 months, on the last wage, with resignation shares, and Article 41. |
| Overtime | Each country’s labour law: Saudi Art. 107 (actual hourly wage + 50% of basic, ÷ 30 ÷ 8 per the HR ministry guide), UAE Art. 19 (basic + 25%, night + 50%, ÷ 30 ÷ 8 per the ministry guide), Qatar Art. 74 (basic + 25%, night + 50%), Kuwait Art. 66 (full wage + 25%, ÷ 26 ÷ 8 per the courts), Egypt Law 14/2025 Art. 121 (+35% day, +70% night; the user picks the hourly method because the law does not set one). |
| Annual leave | Each country’s labour law: Saudi Arts. 109–111 (21 days, 30 after 5 continuous years, balance paid on the actual wage), UAE Art. 29 (30 days, 2 days a month between 6 months and a year, balance paid on the basic wage), Qatar Arts. 72 and 79–81 (3 weeks then 4 from 5 years, after a full year, on the basic wage), Kuwait Arts. 70–73 as amended in 2017 (30 working days, after 6 months, full wage, daily wage ÷ actual working days), Egypt Law 14/2025 Arts. 124–125 (15, then 21, then 30 days, 45 with a disability; the user picks the daily-wage method because the law does not set one). Each service year’s days are spread evenly over that year. |
| Amount in words | Arabic number–noun grammar (gender agreement, the counted-noun forms, dropping the dual nun before a noun) and each currency’s official subunit. |
| Gold | Purity of each karat out of 24 (21k = 87.5% pure gold), with making charges and tax as you enter them. |
| Old rent (Egypt) | The text of Law No. 164 of 2025 on leasing premises (Official Gazette No. 31 bis, 4 August 2025): Articles 2, 4, 5 and 6. |
Dates
| Calculator | Source |
|---|---|
| Hijri dates | The official Umm al-Qura calendar (its tables built into browsers, 1300–1600 AH), noting a possible one-day difference where months start by moon sighting. |
| Ramadan and Eid dates | Umm al-Qura and published astronomical calculations; final dates follow the official moon-sighting announcement in each country. |
| Saudi paydays | The Saudi Ministry of Finance official payroll calendar (the 27th of the Gregorian month; Friday moves to Thursday, Saturday to Sunday, with Eid exceptions). Years without a published calendar use the same rule and are marked “expected”. |
Health and fitness
| Calculator | Source |
|---|---|
| BMI and ideal weight | World Health Organization BMI categories, and the Devine, Robinson, Miller and Hamwi formulas. |
| Calories and protein | The Mifflin-St Jeor equation with standard activity factors; protein from the RDA and the International Society of Sports Nutrition (ISSN). |
| Pregnancy and ovulation | Naegele’s rule (280 days from the last period) adjusted for cycle length, IVF dating from the transfer day, and ovulation about 14 days before the next period. |
| Period | First day of the last period + average cycle length (or the average of earlier start dates), ovulation about 14 days before the next period, normal ranges from Cleveland Clinic, and Ramadan days on the Umm al-Qura calendar. |
| Baby growth | The WHO Child Growth Standards (2006) with daily values from birth to five years, taken from the WHO’s official anthro package, using its z-score method and length/height adjustment. We checked the data against more than 2,500 values in the WHO’s published monthly tables. |
| Pregnancy weeks to months | Gestational age from the first day of the last period (280 days), weeks grouped into months by the common chart used in medical sources, and trimesters ending at weeks 13 and 27. |
| Pregnancy weight gain | Institute of Medicine (IOM 2009) guidelines, used by ACOG: total gain by pre-pregnancy BMI, provisional twin ranges, 0.5–2 kg in the first trimester, then a steady rise to the total at week 40. |
| Body fat | The US Navy formula with American Council on Exercise (ACE) categories. |
| Water intake | A weight-based estimate (30–35 ml per kg) and the European Food Safety Authority (EFSA) reference intakes. |
| Gym | The Epley and Brzycki one-rep-max formulas, National Strength and Conditioning Association (NSCA) charts, and MET values from the 2024 Adult Compendium of Physical Activities with the ACSM equation for calories burned. |
| Heart rate zones | The Tanaka (2001) and Fox maximum heart rate formulas, the Karvonen heart rate reserve method, and the American Heart Association moderate and vigorous ranges. |
| A1C | The ADAG study equation (Nathan et al. 2008) used by the American Diabetes Association: average glucose = 28.7 × A1C − 46.7, the IFCC equation for mmol/mol, and the ADA / CDC categories. |
Study
| Calculator | Source |
|---|---|
| Saudi weighted percentage | High school, Qudurat and Tahsili weights from Imam University’s official admission guide (1448 AH), with the option to enter any other university’s weights. |
| Saudi school holidays | The Ministry of Education’s approved 1448 calendar (including the Makkah, Madinah, Jeddah and Taif calendar) plus the long weekends it announced. The countdown runs to the end of the last school day, Riyadh time; Hijri dates follow Umm al-Qura. |
The general tools (percentages, discounts, GPA, unit conversion, age and others) rely on straightforward maths, and each one explains its method below the calculator.
What we don’t do
- We don’t give medication doses or vaccination schedules; they vary by person and country and belong with your doctor.
- We don’t issue fatwas or give binding legal or financial advice. Results are for guidance; the final reference is the official authority or a qualified specialist.
- We don’t present numbers that change daily (such as currency or gold prices) as fixed; we ask you to enter today’s price.
Found a mistake?
If you notice a wrong result or a law that has changed, write to us from the contact page with the calculator and the numbers you entered. We review every report carefully; fixing errors is a priority for us.