Interior construction tools for immediate use on site.

Gonggan Japsil is an integrated app for interior construction engineers and remodeling contractors, featuring a material calculator, site memo, to-do list, and calculation record. It is designed to allow you to complete estimate calculations and site management on a single screen, covering everything from living room wallpapering to bathroom tiles, paint quotes, and concrete slab mix proportions.

Make calculations that used to be done manually on paper faster and more accurate.

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■ 9 Construction Calculators — Based on Korean Standards

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▸ Tile Calculator — 13 presets based on KS L 1001 standards (instant selection of frequently used sizes such as 300×300, 600×600, etc.). Reflects grout width and loss rate to determine box count and grout volume all at once. Supports 9 colors with 2D drawing view + 3D color preview.

▸ Concrete Calculator — Two modes: Slab and Block. Select mix ratios of 1:2:4 / 1:3:6 / 1:4:8. Calculates cement, sand, and gravel in kg / bag units respectively. Based on Standard Cost Estimation for Construction.

▸ Paint Calculator — 4 paint presets (Emulsion, Urethane, Enamel, Varnish) + standard 2 coats. Minimizes waste using a greedy algorithm for automatic container (0.9L / 4L / 18L) dispensing.

▸ Timber Calculator — Reflects Korean timber market practices using the 'Sai' (才) unit. Converts unit prices for purlins, columns, and rafters, and calculates total costs.

▸ Roofing Calculator — Based on KS F 4910 (Asphalt Shingles). Automatically applies loss rates based on slope and area.

▸ Flooring Calculator — Presets for domestic distribution box sizes for Engineered Wood Flooring, Laminate Flooring, LVT, etc. Supports direct input mode. ▸ Gypsum Board Calculator — Standard KS F 3504 (2.4m · 2.7m). Ceiling and wall modes separated.

▸ Brick Calculator — KS L 4201 + 2021 Standard Cost Estimation for Construction Works. Calculation of brick count and mortar quantity by thickness: 0.5B / 1.0B / 1.5B / 2.0B.

▸ Wallpaper Calculator — Based on LX Z:IN formula. Calculation of 3 types: Narrow-width laminated (53cm) / Wide-width laminated (93cm) / Silk (106cm) + loss rate stages (10/15/20%) + base paper option + wallpaper paste (kg).

All calculations are based on Korean Industrial Standards (KS) and the 2021 Standard Cost Estimation for Construction Works. However, the results are estimates for reference only, and actual construction volume may vary depending on site conditions (openings, material loss, construction methods); expert review is recommended.