Calculate a single vertical row of equally spaced hole centres. Enter the usable vertical distance H between your lower and upper reference boundaries, before subtracting the end offsets. The lower offset A runs upward from the lower boundary to the first hole centre. The upper offset B runs downward from the upper boundary to the last hole centre. Both reported positions are measured upward from the lower boundary.
Enter dimensions in metres: 600 mm = 0.600 m and 50 mm = 0.050 m. Multiply metre results by 1,000 to read millimetres. Hole count includes both endpoint holes and applies to one row.
Use H from 0.001 to 10 m, each offset from 0 to 10 m, and a whole-number hole count N from 2 to 1,000. Dimension inputs use 0.001 m increments. These are calculator entry limits, not woodworking recommendations.
The offsets must also satisfy A + B < H. This cross-input condition must be checked manually: the calculator’s arithmetic operations do not reject overlapping offsets. A zero or negative centre span or spacing is an invalid layout. Fractional hole counts are invalid even if an interface permits them. Unavailable results are not zero and must not be used as dimensions.
Offsets refer to hole centres, not hole edges. This calculation does not determine suitable edge clearance, hole diameter, drilling depth, pin compatibility or shelf load capacity. Displayed precision is not a drilling tolerance. Use the unrounded spacing for layout calculations to avoid accumulating rounding error.
N equally spaced hole centres contain N − 1 intervals. The arithmetic-sequence identity x_N = x_1 + (N − 1)s therefore gives s = (x_N − x_1)/(N − 1). Substituting the chosen endpoints x_1 = A and x_N = H − B gives this calculator’s formula. The general identity is documented in OpenStax, Arithmetic Sequences; its application to these hole-centre coordinates is derived here.
| Vertical distance H | Lower offset A | Upper offset B | Holes N | First position | Last position | Spacing calculation |
|---|---|---|---|---|---|---|
| 0.600 | 0.050 | 0.050 | 11 | 0.050 | 0.550 | (0.600 − 0.050 − 0.050) / 10 = 0.050 |
| 0.900 | 0.060 | 0.040 | 17 | 0.060 | 0.860 | (0.900 − 0.060 − 0.040) / 16 = 0.050 |
| 0.400 | 0.025 | 0.035 | 2 | 0.025 | 0.365 | (0.400 − 0.025 − 0.035) / 1 = 0.340 |
Does this produce a printable drill template?
No. It returns scalar positions, span and spacing for one row. It does not generate a template or a list of every hole position.
Does choosing a hole count guarantee compatibility with a fixed-pitch jig?
No. The resulting spacing is determined by the available span and hole count. Compare the calculated spacing with your jig’s actual pitch before using the layout.
Can the end offsets be different?
Yes. Each offset is measured inward from its corresponding boundary. Their sum must remain less than the usable vertical distance.
Formula source
Production artwork is pending: create and register a 400 × 400 pixel WebP thumbnail, then insert it as the first image block. Use the existing cute yellow five-point star mascot with a cheerful face and hands, floating without separate legs or feet, on a white background with playful navy, blue and teal graphics showing a vertical row of shelf-pin holes and a spacing dimension. Inspect neighboring thumbnails before creating the artwork. No registered thumbnail asset was supplied with this task.