- Display rule.
- Results carry up to 12 significant digits. Between 10⁻¹⁰ and 10¹⁵ they print with comma grouping and at most 10 decimal places (
1,609,344, 167.64, 0.000000001); at 10¹⁵ or above, and below 10⁻¹⁰, they switch to a six-decimal exponential form (9.460730e+15, 1.057001e-25); zero prints as 0. - Stored precision.
- The arithmetic is not rounded at intermediate steps; the 12-digit rule hides binary floating-point noise.
1 m in nanometers reads 1,000,000,000 although the stored double is 999,999,999.9999999, so the last displayed digit is not a guarantee; use the definitions directly for more precision. - Edges and overflow.
- Edges follow from the display rule. At 10¹⁵ and above only seven significant digits are visible, and Enter records what is on screen:
1 ly → Meter shows 9.460730e+15, and Enter on the meter side leaves 9460730000000000 m against the defined 9,460,730,472,580,800 m; the Kilometre row keeps more digits (9,460,730,472,580 km), but only the factor 365.25 d × 299,792,458 m/s is exact. At the small end, 1 nm in light-years reads 1.057001e-25. A result that overflows binary64, such as 1e300 light-years, prints ---; negative inputs convert normally (-5*2 metres is -32.8083989501 ft).