Fractions bring spoken mathematical grammar into direct contact with Indonesian punctuation. Setengah and separuh divide a whole in different discourse settings, per- builds named denominators, a comma introduces decimal digits, and persen turns a value into “per hundred.” The unit after any of them remains invariant.
Setengah, separuh, and seperdua
Setengah is the everyday workhorse for an exact half of a quantity, duration, or unit. It can stand before the noun or measurement it divides.
Tambahkan setengah sendok teh garam ke dalam adonan.
Add half a teaspoon of salt to the batter.
Perjalanan dari rumah ke stasiun memakan waktu setengah jam.
The journey from home to the station takes half an hour.
Saya hanya minum setengah gelas karena tehnya terlalu manis.
I drank only half a glass because the tea was too sweet.
Separuh often presents one part of a contextually given whole or group. It can be exact, but its discourse flavor is “one half/one portion of the whole” rather than a measurement label.
Separuh peserta memilih kelas pagi, dan sisanya memilih kelas sore.
Half the participants chose the morning class, and the rest chose the afternoon class.
Ia menyumbangkan separuh koleksi bukunya kepada perpustakaan desa.
She donated half of her book collection to the village library.
Seperdua is the transparent mathematical fraction “one over two” (academic/mathematical). In ordinary recipes and durations, setengah is more idiomatic.
Pecahan seperdua bernilai sama dengan 0,5.
The fraction one-half has the same value as 0.5.
Building Fractions with per-
For denominators above two, per- attaches to the cardinal denominator. The numerator remains a separate cardinal unless it is se- “one.”
| Written fraction | Indonesian word form | Literal structure |
|---|---|---|
| 1/2 | setengah; seperdua | one per two |
| 1/3 | sepertiga | se- + per- + tiga |
| 2/3 | dua pertiga | two thirds |
| 1/4 | seperempat | se- + per- + empat |
| 3/4 | tiga perempat | three fourths |
| 2/5 | dua perlima | two fifths |
| 7/10 | tujuh persepuluh | seven tenths |
Tiga perempat anggota sudah menyetujui perubahan jadwal.
Three-quarters of the members have approved the schedule change.
Resep itu memakai seperempat kilogram tepung beras.
That recipe uses a quarter kilogram of rice flour.
Dua perlima lahan tersebut digunakan untuk kebun sayur.
Two-fifths of that land is used for a vegetable garden.
The attached spellings sepertiga and seperempat follow the same rule as other se- forms: do not write se per tiga. In dua pertiga, the numerator is separate, but per- remains attached to the denominator.
Fraction Before the Noun or Whole
A fraction normally precedes the unit or noun it quantifies: setengah liter, dua pertiga kelas, tiga perempat panjang tali. The following noun does not become plural.
Tuangkan satu setengah liter air ke dalam panci besar.
Pour one and a half liters of water into the large pot.
Dua pertiga siswa telah mengumpulkan tugas sebelum tenggat.
Two-thirds of the students submitted the assignment before the deadline.
Potong pita itu sepanjang tiga perempat meter.
Cut the ribbon to a length of three-quarters of a meter.
A mixed value can be written 1 1/2 or, more readably in measurements, 1,5. In everyday speech, satu setengah liter is natural; no dan is required.
Decimal Commas
Standard Indonesian uses a comma as the decimal separator. Digits after the comma are normally read individually:
| Written | Read | Value in English notation |
|---|---|---|
| 0,5 | nol koma lima | 0.5 |
| 1,25 | satu koma dua lima | 1.25 |
| 3,14 | tiga koma satu empat | 3.14 |
| 12,075 | dua belas koma nol tujuh lima | 12.075 |
Panjang meja itu 1,25 meter, bukan satu meter penuh.
That table is 1.25 meters long, not exactly one meter.
Termometer menunjukkan suhu 36,8 derajat Celsius.
The thermometer shows a temperature of 36.8 degrees Celsius.
Tangki percobaan menampung 12,075 liter cairan.
The experimental tank holds 12.075 liters of liquid.
The final value is twelve and seventy-five thousandths, not twelve thousand seventy-five. The comma tells the reader that everything following belongs to the fractional part. A point instead groups thousands: 12.075 is twelve thousand seventy-five.
Percentages
Persen means “per hundred.” Write the sign directly after the number: 25%, 12,5%. When spelling out the numeral, write dua puluh lima persen as separate words.
Toko itu memberikan diskon 25% untuk semua tas sekolah.
That shop gives a 25% discount on all school bags.
Dalam survei tersebut, 62,5% responden memilih transportasi umum.
In that survey, 62.5% of respondents chose public transport.
Biaya layanan naik dua persen mulai bulan depan.
The service fee increases by two percent starting next month.
The arithmetic must remain transparent. A 25% discount on Rp80.000,00 is Rp20.000,00, leaving Rp60.000,00.
Setelah diskon 25%, harga tas Rp80.000,00 turun menjadi Rp60.000,00.
After a 25% discount, the Rp80,000 bag falls to Rp60,000.
Sebanyak 12,5% dari 240 peserta berarti tepat 30 peserta.
Exactly 30 of 240 participants is 12.5%.
Ratios and Rates
A ratio written with a colon is read with banding: 3:2 = tiga banding dua. It compares quantities; it is not a decimal or clock time.
Campurkan air dan sari buah dengan perbandingan 3:1.
Mix water and fruit concentrate in a ratio of 3 to 1.
Skala peta itu 1:50.000, dibaca satu banding lima puluh ribu.
The map scale is 1:50,000, read one to fifty thousand.
The separate word per can express a rate: kilometer per jam, dua kali per minggu, Rp5.000,00 per orang. This is a prepositional rate marker, not the attached denominator prefix in sepertiga.
Batas kecepatannya 80 kilometer per jam di ruas jalan itu.
The speed limit is 80 kilometers per hour on that road section.
Kelas renang diadakan dua kali per minggu selama tiga bulan.
Swimming class is held twice per week for three months.
Recipes and Measurements
Measurements favor digits because exact values must be easy to compare. Place a space before an SI unit symbol, but no English plural -s: 1,5 L, 2,25 kg, 750 g. When the unit is written as a word, it also remains invariant.
Resep ini membutuhkan 1,5 L kaldu dan 250 g beras.
This recipe requires 1.5 liters of stock and 250 grams of rice.
Berat paket pertama 2,25 kilogram, sedangkan paket kedua 0,75 kilogram.
The first package weighs 2.25 kilograms, while the second weighs 0.75 kilograms.
Tambahkan seperempat sendok teh merica, lalu cicipi kuahnya.
Add a quarter teaspoon of pepper, then taste the broth.
Indonesian national formatting reverses the punctuation roles familiar from English. 1.250,5 g means 1,250.5 grams. The number-spelling page covers the full convention.
A Quick Arithmetic Check
Fraction expressions must agree with the calculation they describe:
Setengah ditambah seperempat sama dengan tiga perempat.
One-half plus one-quarter equals three-quarters.
Tiga perempat dikurangi seperempat sama dengan setengah.
Three-quarters minus one-quarter equals one-half.
A denominator of zero is not permitted in ordinary arithmetic. 1/0 does not become sepernol as a usable fraction; it is undefined.
Pembagian satu dengan nol tidak terdefinisi dalam aritmetika biasa.
Division of one by zero is undefined in ordinary arithmetic.
Common Mistakes
1. Using an English decimal point
❌ Panjang kabel itu 2.5 meter dalam penulisan Indonesia.
Incorrect Indonesian punctuation — a decimal uses a comma.
✅ Panjang kabel itu 2,5 meter dalam penulisan Indonesia.
The cable is 2.5 meters long in Indonesian notation.
2. Reading decimal digits as a whole number
❌ Angka 4,18 dibaca empat koma delapan belas.
Incorrect standard digit reading — preserve the digits after the comma individually.
✅ Angka 4,18 dibaca empat koma satu delapan.
The number 4.18 is read four point one eight.
3. Separating the fraction prefixes
❌ Se per empat kilogram tepung cukup untuk resep ini.
Incorrect spelling — se- and per- attach in seperempat.
✅ Seperempat kilogram tepung cukup untuk resep ini.
A quarter kilogram of flour is enough for this recipe.
4. Adding an English plural to the unit
❌ Tangki itu berisi 3,5 liters air.
Incorrect language mixing and plural marking — use invariant Indonesian liter.
✅ Tangki itu berisi 3,5 liter air.
That tank contains 3.5 liters of water.
5. Leaving a space before the percent sign
❌ Sebanyak 40 % responden memilih jawaban kedua.
Incorrect standard percentage spacing — the sign follows the figure directly.
✅ Sebanyak 40% responden memilih jawaban kedua.
Forty percent of respondents chose the second answer.
Key Takeaways
- Use setengah for everyday exact halves, separuh for a contextual half, and seperdua in mathematics.
- Build fractions with attached per-: sepertiga, dua pertiga, tiga perempat.
- Indonesian writes 1,25 and reads it satu koma dua lima.
- Write 25% with no space, and distinguish ratio 3:2 from rate per jam.
- Fractional values precede invariant nouns and units: 1,5 liter, not a pluralized unit.
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