The official policy
Bain's official digital-assessment page states that calculators are permitted for the digital assessment (both TestGorilla and Sova) — they are only banned in later case interviews. A pen, paper and a physical calculator are all allowed.
The one nuance for TestGorilla: the platform does not surface an on-screen calculator, so if you want one you have to bring a physical device. Sova candidates report the same policy applies to their numerical section.
What Bain does explicitly prohibit is different: AI tools, recording, screenshots, and any software that transcribes or gives feedback during the assessment. Attempting any of those is a genuine disqualification risk — a physical calculator is not.
Why mental-math speed still matters
Even with a calculator on the desk, the sections are tightly timed and many questions are faster to estimate than to type. Treat mental math as a speed lever, not a workaround for a ban that isn't there. Three drills cover roughly 80% of TestGorilla Numerical Reasoning questions and take 10 minutes a day.
- Percentage change in under 15 seconds: practice (new − old) ÷ old by rounding both numbers to two significant figures first.
- Ratios from messy data: practice converting any two numbers from a chart into a clean ratio (e.g., 8.2 : 12.7 ≈ 2 : 3).
- Reasonableness checks: for every answer, ask 'is this in the right order of magnitude?' before committing. Most wrong answers in timed conditions are off by a factor of 10.
Put it into practice
The fastest way to internalize the format is timed practice that mirrors the real test.
Practice numerical reasoning